STUDIES ON MiCEUAR AND JVIICROEMULSION SYSTEMS

SUMMARY

THESIS SUBMITTED FOR THE DEGREE OF

Bottot of $I)ilosiop|)p IN

CHEMISTRY

BY

SANJEEV KUMAl ^

DEPARTMENT OF CHEMISTRY ALIGARH MUSLIM UNIVERSITY

ALIGARH (INDIA)

1988

S U M M A R Y

The gjroups of chemical compoiuids knovm as surface active

agents are in the most ccaiunon form constituted of a hydro­

carbon portion and a polar or ionic portion in the same mole­

cule. The hydrocarbon portion which can be linear or branched,

interacts only very weakly with the water molecule in an

aqueous environment. Moreover, the strong interactions between

the water molecules arising from dispersion forces and hydrogen

bonding act cooperatively to squeeze the hydrocarbon out of

the water, hence the chain is usually called hydrophobic. The

polar or ionic portion of the molecule, usually termed the

head-group, however interacts strongly with the water via

dipole-dipole or ion-dipole interactions and is solvated.

Consequently the head-group is said to be hydrophilic.

It is essentially the balance between the hydrophobic

and hydrophilic parts of the molecule (ion) rendering -pecial

properties which we associate with surface active agents. The

other common terms used for surface active agents are:

surfactants; association colloids; colloidal electrolytes;

paraffin chain salts; amphipathic compounds; tensides etc.

It should be noted, however, that whereas most detergents are

surface active agents but not all surface active agents are

detergents. The surface active agents, depending on the nature

of the head group, may be classified ctS anionic, cationic,

nonionic and zwitterionic. Both the interfacial properties

and bulk properties of solution of surface active agents are

consistent with the fact that at a certain concentration the

surface active ions in solution associate to form larger

units. These associated units are called micelles. The con­

centration at which this association phenomenon occurs is

known as the critical micelle concentration, usually abbre­

viated to C.M.C. The CMC values of nonionic surface active

agents are usually lower than those of the corresponding

chain length ionic materials.

While stupendous work on surfactants is repojrted in

literature and today thousands of surfactants are available,

studies are still underway to examine various factors respon­

sible for their micellar and adsorption behaviour under

different conditions,

A fundamental understanding of the physical chemistry

of surfactant organized assemblies, their \inusual properties

and phase behaviour is essential for most industrial chemists.

Due to their wide spread use in many industrial applications,

there has been an increasing interest in the surfactant

research, both academic and applied, in recent years, Micellar

systems have attracted considerable interest, owing to their'

potential uses such as in solubilization, reaction media, but

most notably in tertiary oil recovery, Microemulsion systems

are the micellar systems in which air/water interface is

replaced by oil/water or water/oil interface. These systems

are generally made of water, surfactant and with « «,her addi­

tives such as salt, oil and cosurfactant. The nature of

raicroemulsions and the origin of their stability is still a

matter of discussion. Likewise, the role of the cosurfe.ctant is

still underway. In most cases the cosurfactant is a short

to medium chain length alcohol (propanol to hexanol), From a

practical point of view, alcohols have been used in tertiary

oil recovery because they strongly accelerate the rate at

which these systems reach equilibrium in the polyphasic range

and appear to decrease the adsorption of surfactants in the

pores of the rock in the oil field, thereby increasing the

efficiency and decreasing the cost of the tertiary oil

recovery process. They also prevent the formation of l-iquid

crystalline phases. An understanding of phase behaviour cf

surfactants under various conditions and additives is indi­

spensable in utilizing micellar/microemulsions as reaction

media as well as versatile solvents. Microemulsion phase

behaviour is one of the major factors determining the dis­

placement efficiency of a surfactant flood.

Since microemulsions were first observed, there have

been numerous studies regarding their physicochemical,

rheological and structural properties. Water in-oil micro-

emulsions in particular have been the focus of increasing

attention in recent years. The conference proceedings and

a number of recent papers referred in chapter I serve to '

illustrate the present state of understanding of microstru-

ctures in these systems. Notwithstanding the many studies,

formulation of a consistent theory of microstructure and

phase behaviour has remained elusive.

In this thesis studies on the phase behaviour of a

typical water-in-oil microeraulsion system has been investi­

gated, A preliminary attempt has also been made to study the

effect of some short chain aliphatic amines on the micellar

behaviour of cationic CTAB and anionic SDS surfactants with

the view to explore the future applications of amines in

microemulsion systems. The thesis comprises of five chapters.

Chapter I describes the present state of the subject i.e.,

micellar and microemulsion systems, their formation, stability

and some structural aspects. Detailed knowledge of the exten­

sive researches on the subject carried out by various

researchers and their conclusions regarding the physico-

chemical behaviour of the micellar/microemulsion systems can

be gained from the literature cited in chapter I.

The chapter II describesrthe formation of water-in-oil

icroemulsions composed of a cationic surfactant (C,>.TAB and ID

m

C^. TAB)-water-alkanes {C^-C.) and various isomers of alcohols

at different temperatures, Interfacial paramters of cosur-

factant partitioning in the various phases of microeiftulsion

droplet and surrounding were determined from the Schulman-

Bawcott type titration study. The free energy change, A G

for the transference of alcohol from the continuous oil phase

to interfacial region was calculated frcxn the interfacial

parameters of alcohol^It was found that alcohol partitioned

preferentially at the interface with increasing chain length

of oil and decreasing chain length of emulsifier. The negative

value of ^ G° suggests that microemulsions form spontaneously.

The low values of AG° describes that there is only weak inte-s

raction required between surfactant and cosurfactant for

microemulsification.

When the amount of water was increased, the appearance

of microemulsion changed from clear to bluish to turbid.

These transitions were identified on the basis of both resis­

tance measurements and visual appearance. Changes in specific

resistance with water composition were explained in the light

of transition in the water structure from that of spheres to

cylinders to lamellae leading to the phase separation. The

critical moles of water/mole of oil, Vc values, at which the

microemulsion remains stable, was calculated from viscosity

measurements. The Vc values for microemulsion systems were

found to vary with the alkyl chain of oil phase in the

system indicating the water pool size in the microemulsion

droplet increases with the chain length of alkanes.

Chapter III describes the phase behaviour of the

sodiumdodecylsulfate/pentanol/water/benzene system. To examine

jthe effect of salinity on the system, various ternary phase

diagrams in the presence of sodium chloride have been produced

at 25°C. The phase diagrams show existence of various phases

as a result of variation of composition of the system.) Throu­

ghout the duration of this study the surfactant/pentand ratio

(weight/weight) was maintained constant (0.45). Six major phase

regions have been identified in the phase diagram. These

include; (I) liquid in contact with precipitated SDS region

(S+L), (II) a clear homogeneous region (L), (III) unstable

emulsion region (E), (IV) a liquid cyrstalline gel phase (G),

(V) a two phase region, one of the phases, a liquid crystal

and the other a clear liquid (L+G) and (VI) a very narrow

clear region (L*) between L+G and E regions. The L region was

assumed to cons is* of L (water poor) and L^ (water rich)

regions.(The effect of brine concentration on various phase

regions of the phase diagrams was studied in the light of

structural changes and inversion of phases. When the salinity

in the system was increased all the mesomorphous phases- U^u'

L' and the L .p regions either disappeared or were strongly

reduced with respect to the one obtained with pure water.)The

progressive decrease in the area of L^p and It._ regions with

the progressive increase of salinity in brine phase has been

explained due to the decreased solubility of water/or oil in

the microemulsion phase. Various overall compositions were

chosen within the L region and the effect of sodiumchloride

concentration was studied on phase separation and phase

volumes of various phases. The nature of the separated phases

has been also described. This phase separation study gave a

qualitative idea about the existence of various type of

aggregates present in the region. The existence of various

microstructures in the L region was further confirmed by

conductivity measurements by varying the concentration of

water and/or benzene at several compositions of the system.

The existence of different microstructural droplets which

may be either w/cyo/w or w/oil-like microemulsions with

mixed spherical and lamellar structures in the L region have

been detected from conductivity behaviour of the solutions.

Chapter iv describes the water solublllzing capacity of

water-in-oil microemulsions formed by soaps of fatty acids as

emulsifiers. The water solubilizing capacities of soap micro­

emulsions have been compared with those of cationic and anionic

surfactants used as emulsifiers. The effect of branching in

cosurfactant chain and chain length of oil, alcohol and

surfactant on the water solubilizing capacity of micro­

emulsions has been also investigated. Water solubilization

limit of microemulsion system was found to depend upon the

chain length of constituent components and also upon

emulsifier/cosurfactant/oil combination. Branching in the

cosurfactant chain decreased the water solubilization in

the system. The solubilization behaviour has been inter­

preted in terms of partitioning of alcohol among oil, water

and the interface depending on the chain length of oil and

surfactant, as well as molecular packing at the interface

in relation to the disorder produced due to branching in

the cosurfactant chain. The partitioning behaviour of

alcohols was studied by oil-alcohol titration carried out

according to Bowcott and Schulraan, The molar ratio of alcohol

to soap at the interface was found to increase with oil chain

length and decrease with surfactant chain. The values of

free energy change, ^ G , for the transfer of alcohol from

oil phase to the interfacial region were found dependent

linearly upon the chain length of oil and nearly independent

of emulsifier chain. The free energy contribution per methylene

group (CH^) of oil phase for the transference of alcohol was

found 250 J/mole. The dependence on the chain length of oil

and branching in the cosurfactant chain shows that alcohol

partitioning at the interface dictates the increase or

decrease of electrical resistance of the system. The variation

of electrical resistance of the system was also studied in

terms of amount of alcohol in the system. It was found that

by the addition of alcohol in the microemulsion system, the

resistance of the system dropped rapidly and then attained

a constant value. The amount of alcohol at which the resistance

attained a constant value corresponds to the saturation of

the interface in the microemulsion droplet. This critical

amount of alcohol necessary to saturate the interface was

found to increase with the chain length of oil. The initial

fall of resistance was interpreted due to the increase of

degree of ionization of soap molecules by the addition of

alcohol in the system.

/Chapter V describes(the preliminary results obtained

on the micellar behaviour of ionic surfactants in presence of

some short chain amine-water mixtures. The CMC values of

CTAB, CPC and SDS were found to decrease by the gradual

addition of amines in small concentrations. The CMC lowering

effect of amines was explained in the light of structural

promotion of water in presence of small concentration of

amine with concomintant increase of driving force for micelle

formationJ^The magnitude of CMC decreasing effect of amines

was found to be much higher as compared to the corresponding

alcohols. However, similar to alcohols the CMC of surfactants

were found to decrease with increase in the chain length of

amine. This effect was explained on the basis of the fact

that the increased alkyl portion of the amine molecule

promotes the driving force for association, A large decrease

in CMC of CPC than of CTAB in presence of same concentration

1»

of amine in the system was explained in the light of delcca-

lization of charge and decreased charged shielding et C?C

micelle which affect interaction with amine and therefore the

CMC.

STUDIES ON MICELLAR AND MrCROEMULSION SYSTEMS

THESIS SUBMITTED FOR THE DEGREE OF

Sottor at Sj^U^osiopW IN

CHEMISTRY

BY

SANJEEV KUMAR

DEPARTMENT OF CHEMISTRY ALIGARH MUSLIM UNIVERSITY

ALIGARH (INDIA)

1988

T3602

9*0 Wy

%spcef ccf S'caefcr

C)r. JiarnaficTaD Singfi

Dr. H.N. Singh Reader

vjjev DEPARTMENT OF CHEMISTRY ALIGARH MUSLIM UNIVERSITY

AUGARH-202001

PHONE : Office : SSIS

Ua/e....li8fA9.»?.S'

This is to certify that the thesis entitled, 'Studies

on Micellar and Microemulsion Systems', is the original

work carried out by Mr. Sanjeev Kumar under my supervision

and is suitable for submission for the award of Ph.D.

degree in Chemistry.

"^H^ (H.N. Sin^)

ACKNOWLEDGEMENTS

I thank Dr. H.N, Singh, Reader, Department of Chemistry,

for his supervision. He was more than a supervisor to me and

was my mentor, philosopher and guide. As one of my most res­

pected teachers he strove hard to introduce me to the realms

of knowledge and helped me grow and branch out. His premier

support, constructive criticism and humble patronage will

always be a cornerstone of my life.

I place, on record my deepest gratitude to Professor

S.M. Osinan, Chairman, Department of Chemistry, Aligarh Muslim

University, Aligarh, for providing the necessary facilities

for this work,

I am extremely beholden to my parents for their affec­

tionate encouragement and interest in my academic pursuits.

I acknowledge the help offered to me by my friends, and

lab. colleagues, Mr^ Ch. Durga Prasad, Mr, Sharad Tiwari and

Mrs. Sangeeta Kumar.

I thank the University Grants Commission for a research

grant.

Last, but by no means least, I thank my wife Sudha for

her constant help, encouragement and devotion, which has been

so reassuring and helped me to "make it".

UJEEV KUMAR)

CONTENTS

LIST OF TABLES

LIST OF PUBLICATIONS

PAGE

(i)

LIST OF FIGURES (viii)

(Xi)

LIST OF PAPERS PRESENTED IN CONFERENCES (xii)

CHAPTER

I GENERAL INTRODUCTION 1

II EFFECT OF CHAIN LENGTH OF ALKANES ON

WATER-IN-OIL MICROEMULSIONS 33

EXPERIMENTAL 36

RESULTS 41

DISCUSSION 65

III EFFECT OF BRINE CONCENTRATION ON THE

PHASE BEHAVIOUR OF SODIUM DODECYLSULPATE/

PENTANOL/WATER/BENZENE SYSTEM 73

EXPERIMENTAL 78

RESULTS 81

DISCUSSION 97

IV INFLUENCE OF ALKYL CHAIN BRANCHING OF

COSURFACTANT ON MICROEMULSION STRUCTURE

AND SOLUBILIZATION 108

EXPERIMENTAL 111

RESULTS 115

DISCUSSION 138

V MICELLAR BEHAVIOUR OF IONIC SURFACTANTS IN WATER-ALKYLAMINE MIXTURE 147

EXPERIMENTAL 153

RESULTS 155

DISCUSSION 168

REFERENCES 172

LIST OP TABLES

CHAPTER II PA

TABLE 1 ; Moles of alcohol per mole of surfactant, n /n , a s

and moles of oil per mole of surfactant, n /n .,

for the microemulsion system composed of 1 g

CTAB (Fix)+ n-pentane + Ig water (Fix)+ 2-ethyl-l-

hexanol at various temperatures. 43

TABLE 2 : Moles of alcohol permole of surfactant, n /n , o S

and moles of oil per mole of surfactant,n /n , ^ o' s

for the microemulsion system composed of 1 g

CTAB (Fix)+ n-hexane + Ig water (Fix)+ 2-ethyl-

1-hexanol at various temperatures.

44

TABLE 3 : Moles of alcohol per mole of surfactant, n /n , a s

and moles of oil per mole of surfactant, n /n , w 5

for the microemulsion system composed of 1 g

CTAB (Fix) + n-heptane + 1 g water (Fix) + 2-

ethyl-1-hexanol at various temperatures.

45

TABLE 4 : Moles of alcohol per mole of surfactant, n /n ,

and moles of oil per mole of surfactant, n /n , w 5

for the microemulsion system composed of 1 g

MTAB (Fix) + n-pentane + 1 g water (Fix)+ 2-

ethyl-1-hexanol at various temperatures. 46

TABLE 5 : Moles Of alcohol per mole of surfactant, n /n ,& d s moles of oil per mole of surfactant, n /n ,

O S f' r

the 9»icroemulsion system composed of 1 g MTAB

(Fix) + n-hexane + 1 g water (Fix) + 2-ethyl-

1-hexanol at various temperatures 47

TABLE 6 I Moles of alcohol per mole of surfactant, n /n , cl S

and moles of oil per mole of surfactai&t, n /n ,

for the microemulsion system composed of 1 g

MTAB (Fix) + n-heptane + 1 g water (Fix) + 2-

ethyl-1-hexanol at various temperatures 48

- ii -

TABLE 7 : Mole fraction of alcohol at the interface

(X^) and in continuous phase (X°), slope (K), a a intercept (I), for the microemulsion system

composed of 1 g CTAB (Fix) + 1 g water {Fix)+

n-alkane + 2-ethyl-l-hexanol at various

temperatures 52

TABLE 8 : Mole fraction of alcohol at the interface

(X ) and in continuous oil phase (X_), slope

(K), intercept (I), for the microemulsion

system composed of 1 g MTABXFix)+ 1 g water

(Fix) + n-alkane + 2-ethyl-l-hexanol at

various temperatures. 53

TABLE 9 : Variation of standard free energy (AG )

of transfer for alcohol from oil phase to

interfacila region with oil, surfactant chain

length and temperature. 54

TABLE 10: Effect of water concentration on the specific

resistance of the microemulsion system composed

of 1 g CTAB (Fix) + water + 20 ml n-alXane

(Fix) + 2-ethyl-l-hexanol at 25+0.1°C 56

TABLE 11: Effect of water concentration on the viscosity

(^ ) of microemulsion system composed of 1 g

CTAB (Fix)+ water + 20 ml n-alkane (Fix) +

n-octanol at 25+0.1°C. 57

TABLE 12: Effect of water concentration on viscosity

{\) of microemulsion system composed of 1 g

CTAB (Fix) + Water + 20 ml n-alkane (Fix) +

2-ethyl-l-hexanol at 25+0.1°C.

TABLE 13: Effect of water concentration on the viscosity

(' ) of microemulsion system composed of 1 g

CTABiFix)+ water + 20 ml n-alkane + n-pentanol

at 25+0.1°C.

- iii -

TABLE 14: Effect of water concentration on the viscosity

{ ""l ) of microemuls ion system composed of 1 g

CTAB (Fix) + water + 20 ml n-alXane + iso-

pentanol at 25+0.1°C. 61

TABLE 15: Variation of critical n^n^ (V^) ratio for

the various microemulsion systems against the

alkyl chain length of oil and isomer of

alcohols. 63

CHAPTER III

TABLE 1 :

TABLE 2

TABLE 3 :

TABLE 4

TABLE 5

Effect of salinity of the phase volxanes, ,

of separated phases of the system: 1 g SDS-

2.23 g n-pentanol-10, 30 and 45 weight percent

of benzene and 30, 20 and 15 weight percent

of brine 87

Variation of conductance against the weight

percent of components in the system contain­

ing 1 g SDS-2.23 g n-pentanol-0,17 g benzene

and water at 25°C. 89

Variation of conductance against the weight

percent of components in the system containing

1 g SDS-2,23 g n-pentanol-1.74 g beneeae and

water at 25°C. 90

Variation of conductance against the weight

percent of components in the system containing

1 g SDS-2.23 g n"-pentanol-0.17 g beneene and

water at 25* C. 91

Variation of conductance against the weight

percent of components in the system containing

1 g SDS-2.23 g n-pentanol-0.81 g water and

benzene at 25°C. 93

- iv -

TABLE 6 : Variation of conductance against the weight

percent of components in the system containing

1 g SDS-2.23 g n-pentanol-1.38 g water and

benzene at 25°C- 94

TABLE 7 : Variation of conductance against the weight

percent of components in the system containing

1 g, SDS-2.23 g n-pentanol-1.74 water and

benzene at 25°C. 95

CHAPTER IV

TABLE 1 : Water solubilization limit of normal and branched

chain alkanol microemulsion composed of 1 g soap

(Fix) + 10 ml n+alkane (Pix)+ water + 8 ml

alkanol (Fix) at 30°C. IIC

TABLE 2 : Water solxibilization limit of normal and branched

chain alkanol microemulsion composed of 2 g

sodixim stearate (Fix)+ 10 ml n-alkane (Fix)

+ 8 ml alcohol (Fix) and water at 30°C. 117

TABLE 3 : Water solubilization limit of normal and branched

chain alkanol microemulsion composed of 1 g

surfactant (Fix) + 10 ml alkane + water + 5 ml

cosurfactant at 30°C, 118

TABLE 4 :

TABLE 5 :

Moles of alcohol per mole of soap« n / n , a s

and

for the moles of oil per mole of soap, ^e/^s' microemulsion system composed of 1 g sodixim

stearate (Fix) + 3 ml water (Fix) + n-ajkane +

isomer of pentanol at 30°C. 119

Moles of alcohol per mole of soap, n /n -and o S

moles of oil per mole of soap, n /n , for the

microemulsion system composed of 1 g sodium

palmitate (Fix) + 3 ml water (Fix)+n-allcane +

isomer of pentanol at 30°C. 121

- V -

TABLE 6

TABLE 7

Moles of alcohol per mole of soap, n /n , and moles of oil per mole of soap« n /n , for the

o s

microemulsion system composed of 1 g sodlxim

myristate (Fix)+3 ml water (Fix)+n-alkane+

isomer of pentanol at 30 C, Mole fraction of alcohol at the inter-face (X^)

and in continuous oil phase (X_), slope (K),

intercept (I) and A G ^ for the microemulsion

system composed of 1 g sodium stearate (Fix)

+ 3 g water (Fix)+ n-alkane + iscxner of

pentanol at 30°C.

123

125

TABLE 8 : Mole fraction of alcohol at the interface (x!) and in continuous oil phase {X_), slope (K),

_ a

intercept (I) and A G for the microemulsion

system composed of 1 g sodium palraitate (Fix)

+ 3 g water (Fix)+ n-alkane + isomer of pentanol

at 30°C, 126

TABLE 9 : Mole fraction of alcohol at the interface (x^) -. a

and in continuous oil phase (X 0, slope (K),

intercept (I) and A G for the microemulsion

system composed of 1 g sodixim myristate (Fix)

+ 3 g water (Fix)+n-alkane +isomer of pentanol

at 30°C. 127

TABLE 10: Effect of water/oil ratio on the resistance of

microemulsions composed of 1 g sodixim stearate

(Fix) + water + 10 ml n-alkane + 8 ml isomer of

pentanol at 30°C. 130

TABLE 11: Effect of water/oil ratio on the resistance of

microemulsions composed of 1 g sodium palmitate

(Fix) + water + 10 ml n-alkane (Fix) + 8 ml-

isomer of pentanol (Fix) at 30 c. 132

- VI -

TABLE 12: Effect of water/oil ratio on the resistance

of microemulsions composed of 1 g sodivim

myristate (Fix)+ 10 ml n-alkane (Fix) +

water + 8 ml isomer of pentanol (Fix) at 30°C, 134

TABLE 13: Effect of alcohol concentration on resistance

of microemulsion composed on 1 g sodium

stearate (Fix)+ 3 ml water (Fix)+ 10 ml n-

alkane (Fix) + isomer of pentanol at 30°C. 136

CHAPTER V

TABLE 1 : Variation of conductivity, K, with concentration,

C, of CTAB in different concentrations of ethy-

lamine in water at 30°C. 156

TABLE 2 : Variation of conductivity, K, with concentration,

C, of CPC in different concentrations of ethy-

lamine in water at 30 C. 158

TABLE 3 : Variation of conductivity, K, with concentration,

C, of SDS in different concentrations of ethyla-

mine in water at 30°C, 160

TABLE 4 : Variation of conductivity, K, with concentration,

C, of CTAB in different concentrations of propyla­

mine in water at 30 C. 162

TABLE 5 : CMC values of CTAB, CPC and SDS in amine-water

mixtures at 30°C 164

TABLE 6 : Slopes (Ohm~ /ml" ) above and below the CMC of

CTAB in amine-water mixtures at 30°C, 166

TABLE 7 : Slopes (Ohm~ /ml" ) above and below the CMC of

and SDS in ethylamine-water mixtures at 30 C. 167

CHPATER I

- vii -

LIST OP FIGURES

PAGE

FIGURE 1 :

FIGURE 2 :

FIGURE 3 :

FIGURE 4 :

FIGURE 5 :

Various structural models for micelle. 5

Hartley model of a spherical micelle. 7

A. Schematic illustration for the formation

of various structures in surfactant solution

upon increasing the concentration of surfac­

tant. 8

REVERSE MICELLE 11

A cross section of an aqueous normal micelle

with different solubilization site A and B

represent same and upposite charge solute

10 the micelle while C and D represent the

nonpolar and amphiphilic solutes. 13

CHAPTER II

FIGURE 1 :

FIGURE 2 :

FIGURE 3 :

FIGURE 4 :

Plots of n /n versus n /n„ for microemul-a s O S sion systems composed of 1 g surfactant (Fix)-

1 g water (Fix)-n-pentane-2-ethyl-l-hexanol

at 10°, 20° and 30°C. 49

Plots of n /n versus n /n for microemul-a s or a sion systems ccxnposed of 1 g surfactant (Fix)-

1 g water (Fix)-n-hexane-2-ethyl-l~hexanol

at 10°, 20°, 30° and 40°C. 50

Plots of n /n versus n /n^ for microemul-a s V s sion systems composed of 1 g surfactant

(Fix)- 1 g water (Fix)-b-heptane-2~ethyl-

1-hexanol at 20°, 30° and 40°C. 51

Variation of specific resistance as a

function of ' y ater' oil "' ° °^ microemul-

sion composed of 1 g CTAB (Fix), 20 ml oil

(Fix), varying amounts of water and 2-ethyl-

1-lhexanol at 25°C. 55

- viii -

FIGURE 5 : Variation of viscosity (n , ) against n /n

ratio of microemulsion systems cc iposed of

1 g CTAB (Fix)-20 ml n-alkane-water-isomer

of octanol at 25°C. 59

FIGURE 6 : Variation of viscosity (« ) against n /n

ratio of microemulsion system composed of

1 g CTAB (Fix)-20 ml n-alkane (Pix)-water-

isomer of pentanol at 25* C. 62

FIGURE 7 I Plot of critical n^n^ (V^) ratio against

the nvimber of carbon atom (n ) in alkyl

chain of n-alkane. 64

CHAPTER III

FIGURE 1 :

FIGURE 2 :

FIGURE 3 :

FIGURE 4 :

FIGURE 5 :

Ternary phase diagram of the system SDS-

b-pentanol-water-benzene. at surfactant-

alcohol ratio 0,45 (weight/weight). 83

Pseudotemary phase diagram of the system

SDS-n-pentanol-brine (2.0 weight % NacD-

benzene 84

Pseudotemary phase diagram of the system

SDS-n-pentanol-brine (4v0 weight % NaCl)

benzene* 85

Pseudotemary phase diagram of the system

SDS-n-pentanol-brine (6.0 weight % NaCD-

benzene. 86

Effect of NaCl on water rich microemul­

sion L^o of composition: 1 g SDS-2.23 g

n-pentanol-0,58 g benzene-19.26 brine

component. Values indicated C 3 represent

(weight %) of sodi\am chloride in the brine

component 'I' stands for isotropic, 'B' for

birefringent and 'E' for turbid emulsion

phases. 88

- ix -

FIGURE 6

FIGURE 7 ;

Variation of electrical conductance with weight

percent of water in the system: 1 g SDS-2.23 g

n-pentanol and various initial fixed composition

of benzene, 92

Variation of electrical conductance with weight

percent of benzene in the system: 1 g SDS-2.23g

n-pentanol and various initial fixed weight of

water, 96

CHAPTER IV

FIGURE 1 : Plots of moles of alcohol per mole of soap,

n /n , versus moles of oil per mole of soap. Si S

n /n , for raicroemulsion system composed of

1 g sodium stearate (Fix)-3 g water (Fix)-n-

alkane and isomer of pentanol at 30 C.

FIGURE 2 : Plots of moles of alcohol per mole of soap,

n /n , versus moles of oil per mole of soap, o S

n /n , for microemulsion system composed of

1 g sodivum palmitate (Fix)-3 g water (Fix)-n-

FIGURE 3 :

FIGURE 4 :

FIGURE 5 :

alkane and isomer of pentanol at 30 C,

Plots of moles of alcohol per mole of soap,

n /n , versus moles of oil per mole of soap, o S

nVn , for microemulsion system composed of

1 g sodivun myristate (Fix)-3 g water (Fix)-

n-alkane and isomer of pentanol at 30 C, Variation of A G „ with number of carbon atcxn ^ s n , in alkyl chain of n-alkane

Variation of electrical resistance as a

function of water/oil ratio (v/v) in the

microemulsion system composed of 1 g sodium

stearate-water-10 ml n-alkane and 8 ml isomer

of pentanol at 30* C,

120

122

1/4

128,129

131

- X -

FIGURE 6 :

FIGURE 7 :

FIGURE 8 :

Variation of electrical resistance as a

function of water/oil ratio (V/V) in the

microemulsion system composed of 1 g sodixim

palmitate-10 ml n-alkane-water and 8 ml

isomer of pentanol at 30°C, 133

Variation of electrical resistance as a

function of water/oil ratio (V/V) in the

microemulsion system composed of 1 g sodium

myristate-water-lO ml n-alkane and 8 ml

isomer of pentanol at 30 C, 135

Variation of electrical resistance as a

fvmction of volume of alcohol in the

microemulsion system composed of 1 g sodium

stearate-3g water-10 ml n-alkane and isomer o '

of pentanol at 30 C. 137

CHAPTER V

FIGURE 1 : Plots of K Vs C of CTAB in ethylamine-water

mixtures at different ethylamine concentration

at 30°C. 157

FIGURE 2 I Plots of K Vs C of CPC in ethylamine-water

mixtures at different ethylamine concentration

at 30°C. 159

Plots of K Vs C of SDS in ethylamine-water

mixtures at different ethylamine concentration

at 30°C. 161

FIGURE 3 :

FIGURE 4 : Plots of K Vs C of CTAB in propylaroine-water

mixtures at different propylamine concentration

at 30 C. 163

FIGURE 5 : Variation of CMC of CTAB as a function of

amine concentration at 30°C, 165

- xi -

LIST OF PUBLICATIONS

1. Effect of Chain Length of Alkanes on Water-in-Oil

Microemulsions,

J. Surf. Sci. Tech, 2(2), 85 (1986^,

2. Interaction of Thiamine Hydrochloride (Vitamine B^)

with Anionic Surfactants in Aqueous Medixom.

J. Surf. Sci. Tech. 2(2), 115 (1986).

3. Effect of Sodixom Chloride pn Phase Behaviour of

Sodiximdodecylsulfate/Pentanol/Water/Benzene System.

(submitted for publication).

4. Influence of Alkyl Chain Branching of Cosurfactant on

Microemulsion Structure and Solubilization

(submitted for publication)

5. Micellar Behaviour of Ionic Surfactants in Water-

Alkylamine Mixture (To be Submitted).

- xii -

LIST OF PAPERS PRESENTED IN CONFERENCES

1. Solvent Dependence Fluorescence of l-anilino-8-napthalene

Sulfonate and its Application in the Estimation of Polarity

of Micellar-water Interface, In 21st ANNUAL CONVENTION OF

CHEMISTS, Jadavpur University Calcutta, Phv-35. (1984)

2. Effect of Chain Length of Alkanes on W/o Microemulsions, In

2nd National Symp, on Surf, Emul. and Biocolloids, I.I.T. Delhi,

1985, m£7.

3. Phase Diagram and Composition Analysis of System. (SDS-water-

n-Pentanal-Benzene with and without Nacl, Conductivity measure­

ment of single phase in the system. In 73nd Ind. Sci. Cong.

Assoc. Delhi Univ. Jan., 3-7, 1986 (Late Abstract)

4. Formation of W/o Microemulsion : Effect of Natiare of Cosurfactant

and Emulsifier. In 6th International Symp. on Surfactant in

solution. New Delhi, 1986, ME-31.

5. Influence of Oil and Surfactants Chain Length on W/o Microemul­

sions. In 6th International Symp. On Surfactant in solution.

New Delhi, 1986, ME-32.

6. Interaction of sodivim Alkyl sulfates with some Cations of

Biological Importance, In 6th International Symp. on Surfactant

in solution. New Delhi, 1986, BA-35.

7. Organized Media-Mediated Chemiluminescence Methods, Application

in Analytical Chemistry, In 23rd ANNHAL CONVENTION OF CHEMIST,

Annamalai University, Annamalainagar, 1986, Anal.55.

8. Influence of Branched Chain Cosurfactant on the Soluilizing

Capacity of Microemulsion systems. In 3rd National Conference,

on Surfactant, Emulsions and Biocolloids, Dec. 28-30, A.M.U.,

Aligarh, PS9.

9. Effect of Sodium Chloride Concentration on the phase Behaviour

of SDS-n-Rentanal-water-Benzene Microemulsion system. In 3rd

National Conference on Surfactant Emulsions and Biocolloids

Dec. 28-30, A.M.U., Aligarh, 1987, PS-10.

10, Micellar Behaviour of Cetyltrimethylammoniximbromide in water

alkylamine mixture. In76th session of Indian Sc. Cong, Assoc, will

be held at Madurai Kamraj Univ., January 7-12, 1989T

CHAPTER - I

GENERAL INTRODUCTION

Surface Active Agents and Their Behaviour in Solution;

The modification of surface characteristics of fluids

in the presence of substances introduced from outside is of

tremendous utility. Such type of foreign sxibstances derived

mostly from fatty acids, fatty alcohols, alkyl phenols, alky-

lamlnes, mercaptans and from other variety of sources are

known as stirface active agents or surfactants. Surfactants,

surface active agents, also called detergents, are amphiphilic,

organic or organometallic molecules where a polar head group

attached to a long non-polar tail provides distinct hydrophobic

1-3 and hydrophilic functionalities . Owing to the polarity of

the distinct regions these substances have also been referred

4 5 to as amphipathichetferopolar or polar-nonpolar substances ' *

The polar-nonpolar character is responsible for the unique

properties of surfactant molecules in solution v^ich render

possible applications in detergency, cleaning, wetting, flota­

tion, emulsification, dispersion, foaming etc, " The factor

responsible for desired surface activity is the balance between

11 lyophobic and lyophilic characteristics of these molecules ,

Aqueous solutions of surfactants or amphipathic mole­

cules, at a minimum concentration, referred to as critical

micelle concentration (CMC), associate dynamically to form

normal micelles , Depending upon the nature of the hydrophilic

head group, micelles can have either cationic, anionic, zwitte-

rionic or nonionic surfaces. The number of monomers that

aggregate to form a micelle is called the aggregation number

(N) • Typically the CMC's are in the range of 0.01-10,0 nM ,

12 with each micelle consisting of 40-180 monomers , Micelles

do not exist at all concentrations and temperatures. For a

given surfactant at a given temperattire, there is a narrow

concentration range below which aggregation to micelles is

absent and above which association leads to micelle formation.

In other words certain amount of monomers can be accomodated

in the cavities and any further addition of surfactant mono­

mers provides a driving force to minimize contact of the

monomer-hydrocarbon chains with water and resulting in the agg­

regation (micelle formation), This narrow concentration range

during which micelle foirmation occurs is called the CMC.

It is interesting to note that although it is usually

assumed that there is a fairly well-defined water layer around

the micellar surface, there is no agreement on the composition

of the micellar core, i,e,, whether it consists of pure hydro­

carbon or hydrocarbon chains mixed with water. Water penetrat­

ion intothe micellar core is still a matter of controversy.

Many spectroscopic studies indicate that there is significant

escen ,15,16

13 14 pene t ra t ion of water i n to micel les * , Recent f luorescence

s tud ies on the hydrogen bonding in micel lar aggregates"

ind ica t e t h a t the d i s t i n c t i o n between polar and non-polar s i t e s

in the micel le i s inaccurate? in f ac t , i t has been proposed

that micelles are loose and porous structures in which water

17 18 and hydrophobic regions are constantly in contact *

Current thought on this controrersial "water exposxire

of micelles" is founded mainly on low-angle neutron scatte­

ring experiments which allow the study of unperturbed mice-

19 lies . This modern concept discusses the main characteri­stics of the molecular conformation in micelles in terms of

20 the predictions of the "interphase model" . Interphase

theory predictions are in agreement with experimental data

and are particularly consistent with some principal features

19 of micellar structure

lo The micellar core is virtually devoid of water, according

to Langmulr* s original principles of differential solxibi-

n ^ 21 lity

2. Micellar chains are randomly distributed and steric forces

determine the final structure;

3, Contact of the hydrophobic sections of the micelles with

water results from a disorderly structure in which ter­

minal groups or chain ends are near the micellar surface

19 and thus exposed to bulk water .

Although the "water penetration" concept of the

hydrophobic sections of micelles is now less acceptable

than the "water exposure" concept, this controversial topic

22 2 3 is still a matter of debate ' , The exact structure of

I I

O ^ E '^

ilT

•o

E ^ _ o*

tr

' I . I i . ' i l ' l ' . 'n 'C II c ^ l ^ . ' ; . •o

'..V C5fi Qi'i 'l ^ ^ ' " " . ' . T i " I ' ' ' I ' l 1 I I

'-' 'I' . ' iV.

I l ' l I I,

o

•o c o

•o o ^

e £

5 5

C9 T3 O E

O

o> c >— o o a t_ D

I/)

T3 O E I -

«n 3

o 3 o I . o a

o E i -o

% X) o E

"5 I -D • ^ O

I -• * - »

U)

U) 3 O I -o

>

an aqueous micelle is not known with certainty, although

several intelligent guesses have been put forth. Figure 1

depicts some of these models. A conventional representation

of micelle is that by Hartley (Fig, 2) and is more acceptable

and useful for visualization.

Though micelles provide a microscopically hetero­

geneous environment/ they are generally small enough for

the macroscopic properties to approximate to those of truly

homogeneous solutions. Moreover* the surfactant molecules

are in dynamic equilibrium either between two micelles or

between a micelle and bulk water. The hydrophobic interior

of a micelle provides a restricted volume of hydrophobic

space in an aqueous environment.

Surfactant molecules can be considered as building

blocks of micelles. It is possible to obtain various types

of structures of surfactant molecules by simply increasing

the concentration of surfactant in water witii a concomitant

24 change in the size of the aggregates . The spherical

micelles formed near the CMC become cylindricalon.es which

may be converted into a hexagonal packing of surfactant

molecules to lamellar structures by increasing the concen­

tration of surfactant in aqueous nedium. Further concent­

ration increase leads to the conversion of lamellar struc­

tures to hexagonal packing of water cylinders (Figure 3),

_ Hydrocarbon _r~ interior

Aqueous exter ior

Gouy - Chapman layer

Stern layer

Fig, 2 Hart lay model of a sphe r i ca l micelle

8

o (/) •*->

I- O

^ t:

^ I CO

iii D

—> O

CO

1 r CO

a a c o

> U) C D O o •;:

Z o > c

°§

O JO

E *-i_

•i- c

N

— id

(b) (A

o c

x: o x: CO

6 Q

T3 C o

c o

c o a 3

o ^

o c o CD

^ D

ID

T3

•J

•D

(A C o "(A

E o o

o

o c

o s: (A

(A

6 o

c

c o

c o

O N

C7)

l_

o

E D C

It is possible to induce a transition from one structure to

another by changing the physico-chemical conditions such as

temperature, pH or by addition of mono or divalent cation

and other additives in the surfactant solution.

Upon sonication above their phase transition tempe­

rature, many long chain surfactants assemble to form single

or multicomponent bilayer vesicles. Compared to micelles the

kinetic stability of vesicles is much greater as is their

size. Typically their size range 2000-10,000 monomers per

vesicle. Also, they are more "rigid* and can entrap and

retain solubilizates

Surfactants in polar solvents, in the presence of

traces of water, associate to form the so-called reversed/

inverted micelles. The structure of these aggregates is

inverted compared to that of normal micelles and can be

thought of as a surfactant entrapped water pool in the bulk

hydrocarbon solvent. The size and properties of reversed

2 26 29 30 micelles vary with the amovmt of water present ' ' * .

The reversed micellar system can be characterized

31 by a variety of physical techniques such as viscosity ,

32 33 34 35

centrifugation , light scattering , NMR , IR , vapour

pressure osmometry and small angle X-ray scattering .

The reverse micellar size depends on the kind of polar groups

10

of surfactant and the magnitude of their size decrease in

the order,: sulfonate > carboxylate > sulfate . It was repo­

rted that micellar size depends least on solvent character

for anionic surfactant and independent for cationic surfac­

tant . In recent years there has been an increasing inte­

rest in studying structure of aggregates of surfactants in

apolar solvents because of their potential application as

catalysts for chemical reactions, as a simple model for

20

enzymatic reactions / and in the preparation of fine collo­

idal particles ' , A typical reverse micellar represen­

tation is shown in Figure 4,

When more than one surfactant are present in aqueous

solution, they form a mixed micellar system. The surface

activity of a mixed surfactant system is reported to be

41 superior to that of the single one , The properties of

surfactant solutions depend on the structure of mixed

micelle i,e, the size and arrangement of components in the

micelle* In the case of mixed micelles whose components

have the same ionic nature i.e. ionic-ionic or nonionic-

nonionic the structure of mixed micelle is expected to be

similar to that of each single micelle. It means that mixed

micelles are formed in the same manner as the single micelle,

in which specific interactions between different surfactant

molecules have been excluded. Therefore CMC of mixture of

ionic-ionic or nonionic-nonionic surfactants in aqueous

11

(_ C

o o Q. ~ c 2 o o

— 1_ ft) O

o o

•o >> o

•D UJ _ l _ l UJ

I Z O

c -o

'^ C D O

o 1- 0) ft)

i | o B

I/) DC LLI > UJ cc

^

UJ Q:

D O

2 ^

12

solution and also the Kraft point have been predicted the-4.0 A3 •

oretically ' . However, it is difficult to predict the­

oretically the dMC of the mixture of nonionic and ionic

surfactants in aqueous solution because of specific intera­

ctions between components and also because of the difference

in status of hydrophobic and hydrophilic parts of components 44 in the mixed micelles •

However, theoretical equations have been formulated

45 46 to explain the changes in CMC of mixed surfactants '

Pseudophase separation models have been developed to treat

47 mixed micellization in binary surfactant mixtures , Recently

a "mass action" model of mixed micellization was given, which

may be preferred over the simpler pseudophase separation

, ,48-50 model ,

Micelles provide several unique properties which

make their extensive use in many disciplines and have many

51-54 practical applications in analytical chemistry , enhanced

55 56 57

oil recovery and in many other areas ' , The solubili­

zation capacity of micelles make them more useful in a

variety of chemical and photophysical processes. An over­

simplified artistic conception of a cross section of an 58 aqueous normal micelle with different solubilization sites

is shown in Figure 5o Several other unique abilities and

properties possessed by micelles are their capability to

13

BULK WATER

CORE

Fig, 5 A cross section of an aqueous normal micelle wi th d i f fe rent s o l u b i l i z a t i o n site^. A and B represent same and opposi te charge solute to the micelle whi le C and D represent the nonpolar and amph iph i l i c so lu tes ( taken f rom " W-L-Hinze , H.N-Singh, Y. Baba and N.G.Harvey, t rends in ana­ly t i ca l chem is t r y , 3 ( 8 ) , 193 ( 1 9 8 4 ) ^

14

concentrate, compartmentalize, organize and localize reac-

tants/solutes; alter effective raicroenvironments (such as

polarity, dielectric constan-t;, viscosity) about solxibilized

solutes; alter chemical pathv/ays and rates; alter spectral

parameters of solxibilizates; alter photo-physical pathways

and rates; stabilize reactants, intermediates and products,

alter quantum efficiencies; alter the position of equilib-

rixjun (such as dissociation constants) ; alter redox proper­

ties (potentials); maintain product and/or reactant gradi­

ents; separate products (charges) ; alter drastically stirface

properties; be chemically stable, optically transparent,

photophysically inactive, and on the whole, relatively

"nontoxic"•

Microemulsion Systemst

There are difficulties experienced by the researchers

in reaching a common ground on the definition of the term

"microemulsions". A number of definitions have been proposed,

but no clearcut definition emerged. The only common defini­

tion described these clear (or sometimes lactescent) systems

as containing one polar liquid (generally water or saline),

a hydrophobic liquid (the "oil phase"), and a selected (one

or several) surface active agent. These systems are ther-

modynamically stable, isotropic dispersions consisting of

microdomains of oil and/or water stabilized by interfacial

film of surfactants.

15

The word "microemulsion" was originally proposed by

59 Jack H. Schulman and co-workers in 1959 , although the

first paper on the topic dates from 1943 , They prepared

a quaternary solution of water, benzene, hexanol, and

potassivunoleate, which was stable, homogeneous, and slightly

opalescent". These systems became clear by the addition of

a medlxim chain alcohol. In the year between 1943 and 1965,

Schulman and co-workers described how to prepare these

59—68

transparent systems , The summary of the basic observa­

tion is that: when a cosurfactant is titrated into a coarse

emulsion (composed of a mixtxire of water/surfactant in suf­

ficient quantity to obtain microdroplets/oil), the result

may be a system which is low in viscosity, transparent,

isotropic, and very stable. The transition from opaque

emulsion to transparent solution is spontaneous and well

defined. It was found that these systems are made of sphe­

rical microdroplets with a diameter between 60-800 angstroms,

It was only in 1959 that Schulman proposed to call these

systems microemulsionst previously,' he used the terms such

as transparent water and oil dispersions, oleopathic hydro-

micelles, or hydropathic oleomicelles.

Later on it was established that microemulsions or

solubilized systems can exist in equilibrium with excess of

oil, water or both. Winsor referred to these respective

16

equilibria as type I# II and III " , He showed qualita­

tively that the transitions l5p*III«*II are dependent on the

hydrophilic versus lipophilic character of the surfactants

72 (HLB) , salinity, oil composition and temperature. Shinoda

and co-workers experimentally defined these transitions as

functions of temperature and ethylene oxide content for

cosolubilized oil and water systems prepared with nonionic

73—76 surfactants " • The single/2-phase boundaries for type I

and type II systems were described on temperatxire composition

77 78 diagrams * . These boundaries were found to be shifted

with variation in HLB (ethylene oxide content, hydrocarbon

chainlength and added anionic surfactant), oil type and

77-79 added salts , Similar effects were observed by Kon-no

and Kitahara for the solxibilization of water and aqueous

salt solutions in non-aqueous media(Type II systems) by

80 81 82 83 cationic , non-ionic and anionic * surfactants.

In order to explain the "spontaneous" formation of

these microdroplets and their stability, the following

explanation was advanced by s chulman: recall that -jf-surface

pressures can be obtained spontaneously by the monolayer

penetration of an alkyl alcohol or cholesterol monolayer with

ionic surface active agents such as salts of alkylsulfate

and alkylamines and sxibstituted amines injected into the

solution (at constant area of the insoluble monolayer)•

17

The value of 7^-surface pressures at the air/water interface

can reach values of more than 60 dynes/cm (although the

collapse 7^-pressure for single component monolayers on their

own are below 35 dynes/cm)• If the surface pressure is held

constant, or below the 60 dynes/cm but above the 35 dynes/cm,

immediate expansion of the interfacial area takes place as

the molecules of ionic surfactant penetrate the monolayer at

the air/water interface. The analogous penetration of the

mixed film by oil molecules at the oil/water interface incre­

asing the surface area is the basis for the formation of

microemulsions. However, the penetrating pressure in this

case must be greater than the oil/water surface tension j o/yi,

which is always less than J a/w tension of 72 dynes/cm, which

is approximately 50 dynes/cm for aliphatic hydrocarbon and

62 35 dynes/cra for aromatic hydrocarbon compounds .

Therefore, it is progressively easier to obtain nega­

tive interfacial tension for these systems, provided that

the oil molecules can penetrate the interfacial film, Rosano

84 et al measured the change in the water-oil interfacial

tension while alcohol was injected into one of the phases.

It was found that the interfacial tension may be temporarily

lowered to zero while the alcohol diffuses through the inter­

face and redistributes Itself between the water and oil 85 86

phases ' making it possible for a dispersion to occur

18

spontaneously, A sufficiently low positive value of J i is

always better for emulsion (macro-or microemulsion) formation;

nevertheless, below a certain positive small equlibrium value

of i phase separation, sol or gel formation will be produced

but not emulsification,

Schulman referred to a microemulsion with special

87 properties. This idea has been reiterated by, Gerbacia

88 89

Carey and Becher , Other workers consider microemulsions

as solubilized systems or micellar solutions " ; a growing

nxunber in fact refer to the "so called microemulsion", Osipow

in his discussion on transparent emulsions claims that there

is no valid method to distinguish between microemulsions and 90 solxibilized systems , McBain and O'Connor distinguished

91 between solubilization and emulsification , They showed that

in the case of hydrocarbon solubilized in a soap solution,

the vapour pressure of the solubilized material is lower than

that in the bulX phase; such solutions are thermodynamically

stable and their properties are solely dependent upon tem­

perature, composition and pressure. In an emulsion, however,

the vapour pressure of the droplet is actually higher than

the vapour pressure of the bulk.

The phase behaviour of water, oil and surfactant

mixtures is now a subject of considerable importance, pri­

marily because of its importance to oil recovery but also

19

because transparent or translucent phases containing oil and

water together with surfactant (microemulsion) are of scien-

92—103 tific interest . In Winsor' s terminology the simplest

phase behaviour of microemulsion can be divided into three

70 distinct categories • The phase study is convenient for

determining the optimum mixing ratio of the surfactant and

cosurfactant and also for determining the extent of solubi­

lization of oil in water or water in oil in the presence of

a definite amount of total surfactant together with cosur-

104 factant • It also provides contoxir maps for studying the

physical properties such as interfacial properties and

stability of various useful phases,

Palit studied solubilization by a series of quater­

nary ammonium soaps# and found regions in phase diagram

designated S^ and S. which are thermodynamically stable

micellar solutions with water or oil as the continuous phase

105 respectively • He found that when solxibilization is high,

there may be a channel between the two regions S^ and S^*

this channel region shows some properties of the neighbouring

gel or liquid crystalline phase. However, the border line

between the channel and gel phase is not clearly defined.

It is possible therefore that systems in this region were

mixture of the two phases that at equilibrium may separate,

although such a separation process may take a long time .

20

Winsor showed that regions S^ and S_ may be separated upon

increase in temperature and could form a channel between S

and S^^^\

Another group that studied microemulsion phase beha­

viour is that of Ekwall, Friberg and others. They refer to

the L2-region in the phase diagram Which is a solution of

reversed micelles similar to Palit' s S_ region, as the

• socalled microemulsion'. Friberg states that "when the

interphase tension is zero, socalled microemulsions are

formed which cannot be considered time emulsions. There are

solutions with solxdsilized water or solubilized hydrocar­

bons" • In phase diagrams presented by Ekwall et al " ,

there is a sharp borderline between the emulsion region and

Lj or L- regions, NMR study of water peaks in Lj region

showed that this region is stabilized partially due to maximum

109 amoxint of bound water , The correlation of phase diagrams

and emulsion stability was dealt with by Friberg and cowor­

kers , Friberg found that the emulsion stability of a

system will depend on the position of that particular system

114 in the phase diagram • Temperature changes and an addition

of fourth component were fotind to affect the position, and

shape and size of various phases due to structural changes

in the system.

One aspect of phase diagram study that has been some­

what overlooked is the state of the systems. Some systems

21

which have been defined as "very stable" have been shown to

be unstable after sometime, ereas some socalled microemul-

sions show excellent stability, others do separate into two

phases. The question of whether the systems are in equilibrium

or a state of reaching equilibrium at a very slow pace need

attention. It is possible that micellar solutions, L systems,

or microemulsions in certain areas of the phase diagram are

in a metastable state particularly close to phase border. An

optimum system is defined to be one for which the surfactant

rich middle jAiase contains equal volumes of both oil and water

and it has been shown that such systems are optimal or nearly

115—117 optimal with respect to oil recovery , The conditions

under which the surfactant has equal affinity for oil and

118 119 water were found to correspond to those which are type III *

Thus, factors which influence surfactant partitioning between

oil and water also determine the siirfactant phase behaviour,

Microemulsion phase behaviour is often described in

terms of pseudo components which are assiimed to behave as

single component. Pseudocomponent pairs are for example,

surfactant plus alcohol, salt(s) plus water. The effect of

salt(s) on phase behaviour is very pronounced, although brine

120 121 is frequently regarded as a single pseudocomponent ' •

Recently it was shown that each component influences phase

behaviour, which means that phase behaviour cannot be fully

122 described by assuming single phase pseudocomponents ,

II

In winsbr type II systems, a non uniform partitioning

of the system has been observed; namely» the concentration

and composition of the inorganic electrolytes may be different

in the excess brine phase and the brine contained in the

12 3—12 micellar phase ~ o Such partitioning yields difficulties

in representing and Interpreting the phase behaviour of

surfactant-alcohol-brine and oil mixtures by considering brine

as a pseudocomponent. In several cases, pseudophase model

has been proved successful to choose appropriately the pseu-

docomponents able to draw simplified and tractable two-126

dimentional phase diagrams from three-dimentional experi-

121 mental phase diagrams exhibiting quite complex tropologies •

Such simplified phase diagrams, which turned out to exhibit

the overall features of ideal Winsor's diagram, have recently

proven convinient to incorporate the phase behaviour infor­

mation into numerical siraultors for enhanced oil recovery

127 applications •

The effect of inorganic salts on the phase behaviour

of mixtures of water, oil, and ionic surfactant is well known

since the pioneering work of Winsor. In particular special

attention has been devoted to the transition between Winsor I,

III and II systems which can be achieved through a number of

128—132 ways , but changing the salt concentration has been

specially investigated because of its application in the

23

132 133 salinity gradient technique * . I n these systems the

interfaces between the microemulsions and the phases in

excess were found flat by visual observation and appeared

sharp or diffuse for systems far or close to critical points,

respectively, the thickness being always smaller than

1000 ;? . The microemulsion domains were found to be consi-1 ? 2 13R

derably reduced in presence of inorganic salts * because

salt decreases the solubility of water and shrink the micro-

83 emulsion region of the ternary phase diagram , Further,

using viscometry and dynamic light scattering, Bedwell and

Gulari reported that NaCl moderates the attractive interactions

between the microemulsion droplets by making the droplets

136 smaller • The droplets were asstomed to behave more like

hard spheres at low water content for a constant surfactant

to salt molar ratio. It has been concluded that since

soditim chloride being dispersed uniformly in the droplet core

so that it does not have a preferential interaction with the

interior stirface occupied by the surfactant.

An understanding of phase behaviour under various

conditions is indispensable in utilizing microeraulsions as

reaction media as well as a versatile solvent.

Role of Cosurfactant in Microemulsion Systems;

It is intrinsically important to change the HLB of

a surfactant mixture continuously by various devices in order

24

to attain a large solubilization or ultimately complete mixing

104 of hydrocarbon and water with less surfactant . The devices

of cosurfactants, surfactants and their combination yielded

137 very large solxibilization . In most microemulsion systems,

a cosurfactant (or cosolvent) is generally used in combination

with the primary surfactant. The issue concerning the role of

this added component and the understanding of necessity for

adding them has paralleled the research and development of

70 71 microemulsion technology since they were originated ' .

More recent studies for enhanced oil recovery processes have

revealed several different phenomena associated with the

- : , , , . . , , ^ 102,103,134 presence of alcohol in microemulsion systems ' ' ,

The most fundamental role of alcohol is probably its

ability to destroy liquid crystalline and/or gel structures

138

which obviate the formation of microemulsion , Under cer­

tain circximstances, alcohols may be employed not so much as a

required ingrediant for microemulsion formation but instead,

to change surfactant partitioning characteristics or to modify

microemulsion properties to meet a specific application ©uch

as a desire for clarity of solution. In a detailed phase

128 139 behaviour study, Salager * found that alcohol is only

one common controlled variable capable of bringing the sur­

factant formulation to its optimum state, Salter showed that

140 additions of alcohol depress solubilization in microemulsion ,

while others showed that it decreases the sensitivity to

2J

141 composition fluctuations . Presumably, the effects of

alcohol on solvent properties of oil and water, and the

ability of cosurfactant molecules to penetrate the surfactant

interfacial monolayer were among those responsible for the

142 cosurfactant functions , The importance of molecular

kinetic conditions of various components, including alcohol,

during microemulsification have been emphasized by Gerbacia and 87

Rosano . An example was given where the occurrence of a

favourable kinetic regime was necessary for microemulsion

formation. The same line of thought with regard to the

dynamic role of cosurfactant was suggested in the work on

143 micellar solution containing alcohols , The requirement

of alcohols in microemulsion formation has been justified on

the basis of the fact that alcohol molecules are sufficiently

short in length to provide a fast molecular diffusion for

spontaneous emulsification and sufficiently large in size to

provide enough interfecial molecular interaction for good

144 solubilization of water (or may be oil) •

Several authors have stressed the striking influence

of alkanols conformation upon different physico-chemical

properties of water-in-oil (w/o) microemulsion systems '

A thorough comparative study of the electrical conductivity

147 behaviour was performed by Clausse et al , who iK>inted out

that the distinction between microemulsions and cosolubilized

system have been analyzed using the percolation and effective

26

148 149 medium theories ' . At very high concentrations of hydro­carbon the solubilization of water in microemulsion droplet is

strongly reduced owing to the transport of alcohol from the

150 micellesiinto the hydrocarbon part of the solution

Recently it has been reported that the use of hexylamine

as cosurfactant in place of more commonly used medixim chain-

length alcohols holds promise of greatly reducing prohlems

associated with solubilization of water at high hydrocarbon

levels . It was observed that hexylamine gives excellent

water solubilizing capacity at high hydrocarbon levels with

extremely low surfactant and cosurfactant content. One of the

possible factors which could be responsible for the behaviour is

the good solubility of water in cosurfactant coupled with

152

sparing solubility of the cosurfactant in water . The effec­

tiveness of hexylamine as a cosurfactant would appear to hold

great promise for industrial formulations where amines can be

tolerated, Hexylamine does have a pungent odour and all

amines tend to be aggressive. These do pose limitations on

the uses of hexylamine. However, if the factor or factors

responsible for the effectiveness of hexylamine can be unco­

vered, then other compounds may possibly be found which could

be equally effective but have lower undesirable properties.

We see that water is sparingly soluble in pentanol (11%) or

hexanol (8%) while being quite soluble (62%) in hexylamine,

152 but completely miscible with pentylamine . Thus hexylamine

27

is seen to be in an intermediate position between the two

extremes as far as ability to dissolve water is concerned.

Neither of the alcohols nor hexylaraine is appreciably soluble

in water, Hexanol is soluble to the extent of 0.^-0,7% by

152 weight, hexylamine about 1% and pentanol about 1,5% .

Therefore sparing solubility in water maybe a necessary con-

dition for a conqpound to be a good cosurfactant for W/o mic-

roemulsion formation at high hydrocarbon levels, but doesnot

•edi<

.137

seem to be a sufficient condition. These predictions are

quite in agreement with the previous concept

Effect of Water in Microemulsion System s

Depending upon its concentration^water may form water

pool or work as 3 dispersion meditun in microemulsion systems.

It was demonstrated that as the water content of the inverted

micelles was increased, the increase in droplet size was

accompanied by an increase in the ratio of alcohol to surfac-

153

tant in the interface , The importance of such an observa­

tion can be judged from the fact that zero interfacial tension,

considered necessary for microemulsion systems, only occurs

at intermediate values of this ratio. In benzene system this ratio

wac quickly exceeded resulting in a macroemulsion at low

154 water content , In the hexadecane system, because of better

association between oil molecules and tails of the sufactant

species, the aggreqates retained their aggregation status.

23

despite a high ratio, by changing into cylindrical or lamellar

155 micelles • As more water was added to the lamellar micelles,

o/w raicroemulsions were formed • By NMR studies Menger et al

have shown an increase in water pool size by increasing water

contents in a typical microemulsion*

The microemulsions were shown to undergo a series of 157

structural changes as the amount of water was increased . The

158 159 same type of behaviour was reported by Singh et al, '

for a typical microemulsion system* Kojilcano et al, have

shown the morphological change in microemulsion systems upon

dilution with water using fluorescence technique • Lindman

et al. have shown how self-diffusion measurements on water

can be used to study the structxire of such systems. They

suggest that the interaction of surfactant head group and

water greatly influence the transport of water in these

solutions^^^'^".

Effect of Oil in Microemulsions System;

In an earlier work on Aerosol OT systems, it was found

that the solubilization limit of water in the droplet increases

with the increase in the alkyl chain length of hydrocarbons * ,

In contrast, it was also reported that the maximtun water solu­

bilization capacity of microemulsions is independent of hydro-

154 carbon nature • Microemulsion formation and their various

physicochemical and structural properties are also reported

23

159 165 to be influenced by the alkyl chain length of oil ' ,

The alkenes form water-continuous microemulsion at a consi-16.'

derably lower water content than the corresponding alkanes

Small angle neutron scattering studies showed the dependence

of structure of water droplet on the hydrocarbon chain length

of the oil medium • For a long chain length oil it was

found that surfactant aggregation number (N) decreased, went

. through a minimum and then increased as the oil voliime frac­

tion was increased. The initial decrease was attributed to a

change of shape of the aggregates from a possible disc like

168 to a spherical shape • Shah reported that the partitioning

of alcohol and surfactant subtly varied by changing the oil

165 chainlength , Recently Clausse et al. demonstrated that

the nature of the hydrocarbon has little influence on the

configuration of microemulsion pseudoternary domain of a

system whose cosurfactant is either a "long" alkanol (e,g,

1-hexanol) or a typically "short" alkanol (e.g. 1-butanol)

169 but greatly for a medium chain alkanol i.e. n-pentanol .

Role of Surfactant in Microemulsion System:

Surfactant plays a central role in microemulsion

system. Depending on the chemical nature of surface active

agents and the relative constituent proportions, w/o or o/w

systems can be obtained. Ionic surfactant is usually stron­

gly hydrophilic hence ionic surfactant needs lijKjphilic

3ii

cosurfactant for larger sol-ubilization. However, nonionic

surfactants change their phase inversion temperatures (PIT)

gradually with their oxyethylene chain length, so that a

single optimum nonionic surfactant whose PIT is close to a

given temx>erature exhibits large sol\ibilizing power. The

PIT is the temperature at which the emulsifier shifts its

preferential solubility from water to oil when the tempera­

ture is increased. But it is well established that nonionic

surfactant may be a good solubilizer at optimxim temperature

(PIT), but only for a limited temperature rangeo On the

other hand, an ionic surfactant is stable with temperature

104 change but needs higher concentration • If the size of

the hydrophilic and lipophilic groups of the emnilsifier

increases, the CMC will decrease, the aggregation will incre­

ase and the solubilizing power will be enhanced. So in order

to increase the solubilization as well as the size of micelle,

ionic or nonionic surfactants with long hydrocarbon chain

73 170 171 lengths should be used ' * , This conclusion agrees

with the findings by Rosano et al,, i.e. the longer-chain

sodiTim alkyl sulfates require a far small amotint of alcohol

87 to be added and Schulman's recipes with long chain (C.g-C.„)

ionic surfactants were always employed ' •

Depending upon the relative effect of all the components

of the system, ternary systems may be separate into two or

three phases when equilibrium reached. The partitioning of

3i

surfactant determines whether the microemulsion forms in the

upper phase, lower phase, or the middle phase, if it is

118 formed . From a surfactant partitioning in various oil/

water systems. Shah et al. have shown that as the oil chain

length was increased from n-hexane to n-hexadecane, the sur-

119 factant partioning in oil decreased • This surfactant

partitioning is important for water solubilization in w/o

microemulsion system. In more recent studies it was again

confirmed that longer chain quaternary salts are more effec­

tive at solxdailizing water than are the shorter chain

172 compounds , With quaternary salts of equal chain length,

pyridinium salts are more effective at solubilizing water at

high oil concentrations then are corresponding trimethyl

173 salts , This was possibly due to the fact that with the

aromatic pyridinium salts there would be delocalization of

charge as well as less charge shielding than with the tri­

methyl salts. This affect the interaction of surfactant with

water and therefore water sol\ibilizing capacity.

Thermodynamics of Microemulsion Systems;

The concept of thermodynamically stable microemulsions

evolved via the percieved need for a transient negative inter-

facial tension to spontaneously form these systems. Ruckenstein

174 and Chi undertook a rigorous thermodynamic treatment of

microemulsions to obtain information on stability. Their work

indicated that when the free energy change of mixing, G , is

32

negative, spontaneous formation of microemulsions occurs,

whereas ^G is positive, macroemulsion can be produced,

which although thermodynamically unstable, may be kinetically

stable. They found that for a specified composition, it is

possible to foirm thermodynamically stable emulsions of both

type (o/w and w/o) , of one type, or none at all, depending

on the value of specific surface free energy. Moreover, they

wer^ able to account for the size of droplets in thermodyna­

mically stable systems and to predict the occurrence of phase

inversion. Conditions for thermodynamical stability of

J 175

emulsions were considered by Wagner • A number of situa­

tions were described in which the interfacial tension was

zero. Under these circximstances the Gibb' s energy term is

small and may be positive or negative. This was observed

176

earlier by Hartley on the basis of qualitative considera­

tions. In addition, Wagner postulated that a thermodynamically

stable emulsion can be obtained only if the concentration of

surfactant required for zero interfacial tension is lower than

its CMC, He also noted that interfacial tension equal to

zero can occur only at an intermediate ratio of surfactant

and cosurfactant. Detailed thermodynamics of microemulsions with special reference to their structure and phase behaviour

177 has been recently reviewed by Ruckenstein ,

33

CHAPTER - II

EFFECT OF CHAIN MHGTH OF ALKANES ON WATER»IN-OIL

MICROEMULSIONS

3i

It is well known that the structure and formation of

microemulsions in general is dependent upon the nature and

composition of various components. Although substantial

amount of work has been done on the role of medium chain

length alcohols but very scanty and unsystematic work seems

to have been done on the effect of branching in the cosurfa-

ctant chain and the chain length of oil on the structure,

formation and stability of w/o microemulsions.

In this chapter water-in-oil (w/o) type microemul-

sion has been the focus of our studies because this type of

microemulsion provides a very useful system for the study of

water near charged surfaces provided by the polar groups of

the emulsifiers. The studied microemulsion systems were composed

of cationic surfactant, water, various n-alkanes and isomers

of alcohols. The two emulsifiers selected were cetyltrime-

thylammoniumbromide (CTAB) and Myristyltrimethylammonixim-

bromide (MTAB). In order to gain insight into the role of

oil chain length on the thermodynamic stability of microem­

ulsions, the standard free energy of transfer from the con­

tinuous phase to the interfacial region of the cosurfactant

was determined.

Visual appearance of microemulsions from clear to

bluish to turbid was further identified by specific resistance

3^

measurements. The stability of microemulsion droplets for

maximum accximulation of water was identified by viscosity

measurements in terms of critical nxmiber of moles of water

per mole of oil, n /n (V ) values as a function of nature w o c

of alcohol and oil.

36

EXPERIMENTAL

Purification of Surfactants and Solvents:

Cetyltrimethylairanoniumbromide (CTAB) was obtained

from Sigma Chemical Company (U.S.A.), It was purified by

repeated recrystallization with acetone-water mixture and

drying in a vacuum oven at a constant temperature (50°C)

Myristyltrimethylaramoniumbromide (MTAB) was a gift from

Professor Willie L, Hinze of Wake-Forest University, USA,

The sample was used without further purification. However,

the purity of the surfactants was checked from the absence

of minimvun in the concentration versus surface tension plots

and from CMC measurements. Iso-octyl alcohol (2-ethyl-l-

hexanol) was obtained fran Flxika Chemical Company, Switzer-

land.n-Octanol and iso-pentanol were of BDH products of

high purity grade (99%). n-Pentanol was an E.Merck product

(>99%). The hydrocarbons viz., n-hexane and n-heptane were

obtained from BDH (99%) and n-pentane was an E.Merck product

(>99%). All the solvents were used as supplied unless

stated otherwise.

Ordinary distilled water was first d^mineralized

hy passing through an ion exchange column. It was distilled

twice in presence of alkaline permanganate in a Pyrex glass

quick fit assembly. Water equilibriated with the atmospheric

carbondioxide was used for preparing the solutions. The

37

conductivity of the resulting distilled water was in the

6 6 1 range of 1 x 10 to 2 x lO" ohm .

Preparation of Microemulsion Systems :

The method of preparation of a microemulsion system

87 158 159 was the same as described else where ' ' , At constant

temperature, a coarse emulsion was first produced by appro­

priate mixing of surfactant (1 gm), water(lgm), oil (10 or

20 ml). This coarse mixture was then titrated with a cosur-

factant to obtain a clear solution (microemulsion), More

oil was added which turned the system turbid . The turbid

mixture was further titrated with cosurfactant until it

became transparent. This process was repeated to obtain

several experimental points, i.e. microemulsion of various

compositions. The same study was carried out at different

temperatures (10°-40°C). To study the effect of chain

length of emulsifiers on various interfacial parameters of

a microemulsions, CTAB and MTAB were chosen. To prepare

microeroulsions of various compositions, the amount of water

was varied in the each set of experiment, n-pentane,

n-hexane and n-heptane were used as oil phases to study the

effect of alkane chain length on the various physicohemical

properties of microemulsion systems. The effect of branch­

ing in cosurfactant chain (alcohol) on the stability of

33

luicroemulsion systems was studied by using different isomers

of pentanol and octanol. The systems studied were all very

stable and no phase separation occurred even after keeping

them for weeks. The electrical resistance, density and

relative viscosity of the microemulsion system of a given

composition also didnot change with time.

Measurement of Electrical Resistance :

A number of sets of microemulsion systems of various

composition were prepared in separate glass tx:ibes. The tubes

were immersed in a constant temperature water bath maintained

at 25+0,1°C, The electrical resistance of the microemulsion

systems was then measured by a Phillips model PR 9500 condu­

ctivity meter, equipped with platinized electrodes (cell

constant = 0.698 Cm~ ).

Viscosity Measurement :

The viscosities of the microemulsion systems were

measured in a Ubbelohde viscometer therroostated at 25+0.1 C.

The relative viscosities ( \ ) of these solutions were

determined against water (time of flow = 170.1 sec). The

^ of a solution was calculated by using the relation;

ri d t to g. o o

39

Where "*! and d represent the viscosity and density

of the microemulsion, " ^ and d^ are the viscosity and den­

sity of water at the experimental temperature, t and t are

the times of flow for a fixed voliune of microemulsion solu­

tion and water respectively. The density of microemulsion

samples were measured by the following method.

Density Measurement :

For the measurement of density, a dllatometer of

approximately 5,5 ml capacity fitted with a graduated stem

of least count 0,002 ml was used. The marks on the stem of

the dilatometer were calibrated by making use of the den­

sities of purified cyclohexane and water at various tempera­

tures. The volume change of cyclohexane and water during

the calibration of the dilatometer were recorded as a function

of temperature. At a particular temperature density of the

solvent was calculated from the well known density tempera­

ture relation;

d^ = [dg+ 10"ic(t-t3) + 10"^P(t-tg)^+10'^(t-tg)^J+10"'

where d ,oC,fiandyare constants. For cyclohexane these

constants have the following values.

P r d oC P) 'Y Limit of Temperature ^ K / Error Range

0.79707 -0.8879 -0.972 -1.5500 0.0003 0 to 60°C

40

The known amount of the solution (by weight) was

transferred to the calibrated dilatometer and the volxjine

was noted at the experimental temperature and the density

values were then determined for different microemulsion

systems.

RESULTS

The studies of the formation of water-in-oil (w/o)

microemulsion systems composed of surfactant-water-n-alkane

-2-ethyl-l-hexanol, were investigated at various temperatures. n

The molar ratio of alcohol to surfactant, -~— , and oil to n s

surfactant,—2_, were determined by a titration study carried s g7

out according to Schulman and Bowcott . Titration data for

CTAB and MTAB emulsifiers, oils of varying chain length at

different temperatures are given in tables 1-6. The plots of n n —2— versus — ^ at various temperatures are shown in figu-s s res 1-3, From these straight line plots for each system at

various temperatures, the values of slope (K) and intercept(I)

were calculated. The values of I and K represent the moles

of alcohol per mole of surfactant at the interface and moles

of alcohol per mole of oil in the continuous phase respec­

tively. PrcMn these values of I and K the value of mole frac­

tion of alcohol at the interface (X^) and in the continuous

oil phase (X°) were calculated. The value of standard free

energy, A G ° , for transfer of alcohol from continuous oil

phase to intenfacial region was also calculated. The values

of X^, X°, I and K are tabulated in table 7 and 8 and the

values of A G ^ for different systems are given in table 9.

structural changes were studied by varying the com­

position of water in the microemulsion systems composed of

42

1 g CTAB (Fix), water, 20 ml n-alkane and 2-ethyl-l-hexanol. The n

nrunber of' moles of water per mole of oil, - ~ - / was o

plotted against the specific resistance of these systems.

The plots are shown in figure 4, Specific resistances at

different water-oil ratios are tabulated in table 10.

The plots of relative viscosity versus water/oil

ratio in the system for different isomers of oetanol and

pentanol are shown in figure 5 and 6. The viscosity data of

mlcroemulsion composed of different conibinations of oil and

alcohol are tabulated in tables 11-14. The critical water/

oil ratio, V , when the raicroemulsion remains stable, have

been calculated from the sharp inflexion point in the vis­

cosity versus " w ''' ' o plots for different oil-alcohol

combinations. These values are given in table 15. Figure 7

shows the variation of V values with the chain length of

oil in a microemulsion system.

43

Table 1: Moles of alcohol per mole of surfactant, n„/n - and a s

moles of oil per mole of surfactant, n /n , for the

microemulsion system composed of 1 g. CTAB (Fix) +

n-pentane + 1 g water (Fix) + 2 ethyl-1-hexanol at

various temperatures.

n a

" s

10°C

n o n s

n a

" s

20°C

n o n

s

30°C

n a

^s

n o n s

4.96 31.58 4.39 31.58 4.04 31.58

7.76 63.13 7.74 63-.13 6.72 63.13

10.93 94.76 10.12 94.76 9.63 94.76

14.08 126.46 13.07 126.46 12.37 126.46

17.31 158.00 16.24 158.00 15.54 158.00

44

Tabel 2: Moles of alcohol per mole of surfactant, n /n , and

moles of oil per mole of surfactant, n /n , for the

microemulsion system composed of 1 g CTAB (Fix) +

n-hexane + 1 g water (Fix) + 2-ethyl-l-hexanol at

various temperatures.

10°C

"a n s

"o n s

'^a n

s

20°C

'^o n s

30°C

^a n n s s

40°C

^a "o n n s s

5.06 28.34 4 .78 28.34 4.46 28.34 4.18 28.34

7.47 56.69 7.18 56.69 6.91 56.69 6.75 56.69

10.58 86.26 10.03 86.26 9.68 86.26 9.51 86.26

13.72 113.54 13.03 113.54 12.47 113.54 12.32 113.54

16.82 141.84 15.91 141.84 15.29 141.84 15.05 141.84

45

Table 3: Moles of alcohol per mole of surfactant, n /n , and a s

moles of oil per mole of surfactant, "^r/"^ / for the

microemulsion system composed of 1 g CTAB (Fix) +

n-heptane + 1 g water (Fix) + 2-ethyl-l-hexanol at

various temperatures.

n a n s

5.23

8.08

11.22

14.21

16.77

20°C

n o n s

25.85

51.72

77.03

103.83

129.57

"a n

s

5.00

7.15

9.69

12.25

14.71

30°C

n o n s

25.85

51.72

77.03

103.83

129.57

" a

" s

4.73

6.54

9 .01

11.71

14.44

40" °C

n o n

s

25 .85

51,72

77.03

103.83

129.57

46

Table 4: Moles of alcohol per mole of surfactant, n^/n^, and a s

moles of oil per mole of surfactant, n /n , for the

microemulsion system ccxnposed of 1 g MTAB (Fix) +

n-Pentane + Ig water (Fix) + 2-ethyl-l-hexanol at

various temperatures

^a n

s

10°C

"o n s

"a n

s

20°C

""o

"^s

30°C

"a n s

^o n s

11.17 57.83 10.40 57.83 9.13 57.83

13.80 72.30 12.50 72.30 11.10 72.30

16.53 86.73 14.67 86.73 13.00 86.73

18.93 101.23 16.83 101.23 15.30 101.23

21.10 115.70 19.13 115.70 17.17 115.70

47

Table 5: Moles of alcohol per mole of surfactant^ n^/n , and a s

moles of oil per mole of surfactant, n /n , for the O S

microemulsion system composed of 1 g MTAB (Fix) +

n-hexane + 1 g water (Fix) + 2-ethyl-l-hexanol at

various temperatures.

n a n s

10°C

n o n

s

20°C

a o n n s s

30°C

a o n n„

s s

"a n

s

40°C

^ O n s

11.10 51.06 10.38 51.06 9.80 51.06 9.27 51.06

13.50 63.83 12.33 63.83 11.76 63.83 11.02 63.83

15.77 76.57 14.33 76.57 13.70 76.57 12.87 76.57

17.87 89.33 16.30 89.33 15.54 89.33 14.60 89.33

20.03 102.10 18,37 102.10 17.43 102.10 16.40 102.10

48

Table 6: Moles of alcohol per mole of surfactant, n /n , and a s

moles of oil per mole of surfactant, n /n , for the O S

microemuls ion system composed of 1 g MTAB(Fix)+n-heptane

+ 1 g wa te r (Fix) + 2 - e t h y l - l - h e x a n o l a t v a r i o u s

tempe r a t u r e s ,

" a n

s

20°C

n a n s

" a n s

30°C

" o n s

40°C

" a n s

" o n

s

10.30 47 .23 9.80 47 .23 9.27 47 .43

12.22 59.03 11.76 59 .03 11.02 59.03

14.15 70.83 13.70 70.83 12.87 70.83

16.23 82.67 15.54 82.67 14.60 82.67

17.93 94.47 17.43 94.47 16.40 94.47

43

c o

- • -

c Q.

I

c

en

: i c4«n

o o r—

o CO

o ^^

c

o •D N (/) O a E o o

F •4->

o O

•»-> n

, o c O X C9

1 «—

1

CO

o

o

O CD

O CM

O 00

o

o c

c o o O

< • -u D

•5 e

"o

C9

a

o

x: • « j

I

CM

I

CD C

o c a

I u c o I

in .5

tn in c o \n

E ( o t_ o

o c in

in

>

C9

a

en

I

in K

c + c

U) o

o CO

X3

c o 5 D O

CL in c^

( ^ u / ° u ) )UD)OD^jns ^o aiouj jad loqooio ^o saioi^j

50

o o o o ^ CM fO ^J

c o X

I I C

o o

in c »>^ o r

• • - » c o Ci

o

•n » U) o n £ o u 0) E

•« -»

tn >. (/)

c o in -J

E o o '— b

—• o 1_

o X

1

1

-•-» Cb> CM

1 C9 C O X

1 c 1

^^

o

"o

C9 a

C9

X

c «a

in

D

i_

>

in c

o c

o

in •4->

O

Ol

X

LL

o o O <r C

o o o •«j CO u O

H-

D in

o o CM

0 . ^ 2

"LL

( ^u / ' ^u ) juDiOD^jns ^o aiouj j ad IOLJODID ^O saioiAj

51

o o o

C o Q.

I

o o

o CO

o CO

o

o CvJ

o

o o CM

o UD

o CVJ

o CO

o

o

•

^ ^ tn

c

o c

••-> c o o o L. ZJ en o

"6 E (9 a nr o

<•-

o tn C9

o 2

•D

(i) O

a E o o E ^

• » - »

in >» U)

c o

E C9 O i_

o E L .

o «• -

(n c

o c U) 3 if)

C9 >

(A C

o c

»•-

o U)

-»-» o —rf

Q.

CO

o c o K

x: 1

1

>• r. •4-*

C9

CSI

1 (9

c O

••-»

a C9 1

c 1

^^^s

X

LL

•4-»

o ^

en f ^

1 ' ^ K

Li.

• • J

c O •«-» u O i_ D U)

, cn t—

« o

o O v j

T3 C

o o O CO

o O eg • « - »

O

(Su/^u) juD^DDijns ^o aiooi jad 1040010 ^o saio W

i^

Q) a 0

rH

n ^

J.—N.

O (TJ

X • • —

0) m fd ^ a, (0 :3 0 ;3

a •H +J

c o o c •H

Xi

c fO

' H (0 X •—'

a> o fO m M 0) •p a •H

0) ^ +J

-p «0

l - (

0 ^ 0

o r-1 (0

«•-( 0

c 0

-H •p V

p u «w 0)

i H

o s

M 0) +J

m ^ en

t H

+ . - X

•H f^ ^-' CQ < El U

Cn

»H

m 0

•a 0)

w 0

E 0 CJ

E 0) +J CQ > i W

c o •H

w rH 3 E O M O •H

e 0) £ +>

o m

^ -

H -

+J

a. (U

o M 0) •P C •H

• Ul 0) M 3 +J fO M Q) ft E 0) •P

(0 0 0

•H VH

fd > +J (0

i H

o c to X (U

5 1

cH > 1

x: -p <u i

tN

+ <u c (d

> i i H (0 1

c

+ , - v

X •H fX4

>—»

0) G -p

n: I

0) c (d X 0) I G

H m to c I c

II H

o fd o c I c

t^

o (d X

X

=1 (0 C IC

O (0 O

c ic

o (d X

c (d -p c (U I c

X

nJ (0

It H

o Id o c Ic

&

O (0 X

ri (d X

I 2 9) ft (U O E M O 0) P

r-

o

o

o

VO

o

o r-i

o

o

VO

VO

o

o

o

VO

m

o

CX3 o

o eg

CM

% CM

o 1-1

o

o

o VO

o

o

00 o

in

o

T H

T H

« o

o T-i

• o CM

r-

o ^ «

o

CTi O

• o o r

o T-H

• o

CTi O

• o ^ l -VO

o n

o

o

o

in

o

52

% -.—

0 (d X "—'

0) 0} (0 xz 0.

r-\ • H

o (0 0 0 :3 c

• H •P c 0 u c •w TJ C fO

- H (0 > *-~^

(U u (0 *H U <U -P G

• H

(1) ^ +J

+J (0

f-\

0 ^ o o

H (0

IW

o c o •r-\

•p

u (0 1-1

4-1

0) ^ 0 s • •

00

(U M

^ (0 H

X • H

fe v_^

CO < EH 2

cn T- l

4-1 O

-0 0) W O ft E 0 o E 0) +J (0 > 1

m c 0

• H »

nH

0 e 0) 0 ^ u

• H

E

0) ;C •P

U 0 M-i

^ ^ - x

H

-•

•P

a OJ o 1-1 (U •p c

H

% /—V

1^ —-

0) D, 0

nH w

* to (U M ;3 •p 03 U 0) ft E 0 -P

(0 P 0

• H

u «J >

+J (0

l - t

o G (0 X a> £

1 »H 1

i - (

> 1

£ •P 0)

CM

+ <u c m A< i-\

fO 1 G

+ ^^ X

- H P4

• — ^

1 0) p ro ?

D i

T- l

Q) C rO -P ft 0)

c

(U c (0 X 0) K 1 G

0) c rO -P G 0) (X 1 C

•H m n G I G

II H

1 0 (d 0

G I G

II ^

0 (0 X

•H rO X

•rt (Ol W G IG

II H

0 OJI o G i G

II y,

0 (0 X

•H 0 X

•H fo| CO C I G

It H

1 0 m 0 c Ic

II u.

0 fO X

•H (0 X

1 rO U QJ ft Q) U B U O QJ 3

1 t P

GO

r • (N

CM Tj-

• rg

o r-t •

CNJ

00

in

in

o

in

o

CO in

53

VO

00

VO

00

n

00

o • *

• (NJ

r-t - t

•

in •

o 1-1

t

OJ

VO i H

•

00 n

o 00

• r-t

in rH

•

o n

o VO

• T H

-sC T-H

•

n CM

r-\

r-•

o

CO VO

• o

^ VO

• o

VO

o CM

O VO

•<*

n CM

in

o

o O

Q) in rO

JC ft

rH -rH O

e 0 u 4-1

i H

o £ o u

M (0

t l 0 m ^ 0) m w c fd M +J

m 0

' ^ - X

O m O

< '

> i

& U 0) c (0

0) (U M

m -o M ro

TJ C (d -p m

M-) 0

c o

• H + j ro •H l-i

m >

•« o\ 0) rH ^ fO EH

' ^1

d • P

(0 u 0) a E Q) -p

'O

(0

;C +J Di C 0)

•-H

c • H (0

c OJ -p u (0

M-l

:3 to

^ r^ •H 0

^ -p • H

>

c 0 •H & 0) t l

i H (t

-H O 03 m ^t 0) +J C •w 0 •p

-- 0) rH 0 B

^ ;

0 w o <J

1 —

< B 2

^

0 E

\ b «

0 m O

<

1 %-.-»'

CQ < M U

0)

:3 +j (0 M 0) ft e a> H

0)

c (0 •p

ft 0) 3 : 1

c

0)

c fO X 0) X 1

c

0)

c rt) p

c 0)

04 1

c

0) c fd 4J ft 0) X 1 c

0) c: (d X

<u K 1 C

0)

c m •p c

1 c

u 0

1

OJ

r-•

ro

o> •

• n

1

(T> i n

• • > *

i n in •

^t

o rH

i n a\ •

ro

r-CO •

ro

i n vD •

ro

"* 00

t

•*

CM

r •

•

o\ VO

• •>*

o CM

i-H

i H

• ^

»-t

o •

•*

T-H

r-•

m

O rH •

i n

TC

r-•

• ^

CNJ VO

• • ^

o ro

'S" rH

• •

CTi rH

• • *

1

r-o •

i n

i n r-

• • *

1

o •*

54

55

6 o 6 s: o

to

X

o c o

in u

d Hi

Fig. 4

3-0 - (•

2-1*

1-8

1-2

0-6

0-0

—) Clear region

( ) Bluish region ( -) Turbid region

^o.

n - Pentane k n - Hexane o n- Heptane

0-3 0-6 0-9 V2 1-5

" w / %

Var iat ion of specif ic res is tance as a funct ion of

f^water /^oi l f^t 'O o^ microemulsions composed of

1g. CTAB ( Fix ) , 20 ml. oi l ( Fix ) , varying amounts

of water and 2-ethyl - 1 l^exanol at 25°C

c 0 •H CO

i-H

0 e 0) o M V

• H

e 0)

x: -p M-( 0

0) 0 c (0 +J en

T ^

(fl Q) M

u - H U-l • H

u (U ft w 0) x: •p

c 0

c 0

•H •p (0 Ui

+) c 0) o c 0 o w Q) 4J (0 5

»« 0

-p o (U >w «n w

1

> 1

x: + j Q) 1

( N

+ ^ • H

fr<

0)

c to Ai rH

n) 1 c

i H £ o OJ

+ u H) +J

%

+ y * ^

K •H

»-

m < EH U

D rH

M-l 0

•d 0) (0 0 ft

0 u E 0) +J CO > 1 CO

• U

0 T H

• o +1 tn CM

-p m

r-i

B m X (U s: T-i

Xi

EH

0) c IX) -p ft <u a:

0) u c (0 •p to

•rH rH (0 1 Q) E a u

u e •rH x: ^-^ o •rH

u Q) ft (0

0) G ITJ •P C 0) ft I d

0) o c (d •p CO •H "H CO I

(U c m X 0) K 1 C

u •H

m •H

o 0) ft en

O C fd -p CO

• H CO ^ 0) I oj E u •H IW •H

o ft

CO

u

o

vO ) o rH X r~ o

VD

o r-\ X

0^ (N

VD O . H

X CTi • *

vO O i H

X n •<*

v£l

o T H

X VD CT.

»D O T H

X o T H

VD O r-\

X (M

cc

o

VO

CO

VO

o vD

VO

en in

(N

o cc

ON ON 00 IT)

VD VO VD vD VD o f-H

X VO rH

o r H X

VD

n

o r H X cr> r H

O r H

X o in

o T-\

X in r-

o rH

X o ro

O r H

X (TV CD

<N

CM o QD

o in CM

o r H

X •^ CTi O

VD O r H

X r H in

VO

o r H

X CO CO

VO O r H

X r H VD

VO O r H

X (» o

VD O rH

X o • *

VD O rH X

VO CM

CN

n (» >5j'

•<* VO

O <»

vD 0>

CM rH

CM •^

57

of Table 11: Effectv'water concentration on the viscosity { t) of

microemulsion system composed of 1 g CTAB (Fix) +

water + 20 ml n-alkane (Fix) + n-octanol at 25+0.1°C

n-Pentane n-Hexane n-Heptane

(C?)

0.74

0.76

0.78

0 .85

0.92

1.03

n w ^o

0.32

0 . 4 8

0 .64

0 . 8 0

0 . 9 6

1,12

1.21

(A>)

0 .40

0 . 4 1

0 .44

0 . 4 6

0 .53

0 .56

0 . 6 0

n w n o

0 . 3 6

0 .54

0 . 7 2

0 . 9 0

1.07

1.25

1.47

(CP)

0 . 5 2

0 . 5 4

0 . 5 8

0 . 62

0 . 6 8

0 . 72

0 . 8 0

n w ^o

0 . 4 0

0 . 6 0

0 . 8 0

0 .99

1.19

1.39

,.

58

Table 12: Effect of water concentration on the viscosity (r\) of

microemulsion system composed of 1 g CTAB (Fix) +

water + 20 ml n-alkane (Fix) + 2-ethyl-l-hexanol at

25 + 0.1°C

n w n o

0.32

0.48

0.64

0.80

0.96

1.12

i;42

n-Pentane

Viscosity

'^ (CP)

0.51

0.55

0.61

0.67

1.20

1.82

2.20

n w n o

0.36

0.54

0.72

0.90

1.07

1.25

1.44

n-Hexane

Viscosity

^(CP)

0.65

0.71

0.76

0.84

0.91

1.09

1.25

n w n o

0.40

0.60

0.80

0.99

1.19

1.39

1.59

n-Heptane

Viscosity

"n.(CP)

0.86

0.94

1.02

1.14

1.27

1.45

1.66

59

fit c O

••-»

r (« CL

1 C

•

C9 c o K C9 I

1

c ^

(9 c O

• « - >

Q. C9 I

1 C

e

o c

en

c o

E O L. U

O

o L.

C9 C

o o I

c

•^->. o

C I

U) • -

c u.

"at

o

o

"o E t_

a L .

in 0 u in "> <4-

0

1_ 0

••-»

n i _

0 >

• 0

in 0 a h 0 0

u> t -»-» l/> >» in

, 0 c 0 0 0

0

L.

K 0 t.n

Lf)

L L

( "^^ l i ) A^isoos! A

60

Table 13: Effect of water concentration on the viscosity ( )

of microemulsion system composed of 1 g CTAB (Fix) +

water + 20 ml n-alkane + n-pentanol at 25+0.1°C.

n-Pentane

n w n o

0.16

0.24

0.32

0.40

0.48

0.64

Viscosity 7j (CP)

0.44

0.48

0.55

0.66

0.83

0.94

n-Hexane

"w n o

0.18

0.27

0.36

0.54

0.72

0.89

Viscosity -n (CP)

0.57

0.68

0.76

1.05

1.56

1.89

n-Heptane

' w n o

0.20

0.40

0.60

0.80

0.99

-

Viscosity T] (CP)

0.84

1.03

1.46

1.74

2.16

-

6 1

Table 14: Effect of water concentration on the viscosity (rj) of

microemulslon system composed of 1 g CTAB (Fix) +

o. water + 20 ml n-alkane + iso-pentanol at 25+0.1 C.

n w

"o

n-Pentane

Viscosity n w "o

n-Hexane

Viscosity

Y^CCP)

n w n o

n-Heptane

Vis cos ity

r]_(CP)

0.16 0,45 0.18 0.58 0.20 0.79

0.24 0.49 0.36 0.75 0.30 0.88

0.32 0.58 0.45 0.93 0.40 1.00

0.40 0.69 0.54 1.09 0.50 1.22

0.48 0.80 0.72 1.28 0.60 1.38

0.56 0.92 0.89 1.56 0.70 1.54

0.72 1.05 1.08 1.88 0.80 1.74

- - - - 0.90 1.75

- - - - 1.10 1.88

I_

C9 C

o r N Q.

C

•

C9 C

o C» I

c

^

C9

c O a Cd X

c

e

l_

CM

O c o c

Q. I

o 0)

o c o c

Q. ) c

en

CM

CO

o

6

CM

6

CO

6

CO

6 to

6

6 CvJ

6

o

o c

6 ^ "o o

"o

a

C9

o

in

o

o c o

•4->

c

Q.

E o in

•«->

o

•4- I

62 E

•»->

>. tn

c o

"D E (9 o u u E o

o

o

o c

•? ^

i i .

c o

1

c

(n c O en o

a u

o CM

ii.

u o o tn

c o

o >

li-

CD < »-

o

en

X)

o ° Q. IT)

E ^ o H-.

CJ> CO

6

( d ^ l j ) A^jSODSJA

63

Table 15: Variation of critical n /n_ (V ) ratio for various w O C

microemulsion systems against the alkyl chain length

of oil and isomers of alcohols.

n-alkane n-Pentanol iso-Pentanol n-octanol 2-ethyl-l-hexanol

(V^) (V^) (V^) (V^) c c c c

n-Pentane 0.28 0.32 0,53 0.83

n-Hexane 0.37 0,42 0.67 0.94

n-Heptane 0.44 0.49 0.83 1.04

64

.9 • • ->

o

>

o c

c

o

o

Fig.7

•

1-0

0-8

0-6

0-4

0-2

r\.n

rf • n-Pentanol

^^.y"^ 0 Iso-Pentanol ^ y ^ • n-Octanol

j ; ^ ^ - / ^ D Iso-Octanol ^ ' ^ ^

- / ^

- ^ , ^ ^ : : ^ ^

1 1 1 1

n,

8

Plot of c r i t i ca l H ^ / H Q ( V ^ ) rat io against

the number of Carbon atom ( n^ ) in alkyl

chain of n-alkane

65

DISCUSSION

The present microemulsion system may be considered

to be composed of three phases, namely, continuous oil phase,

dispersed water phase and the interfacial region. The dis­

tribution of total alcohol (n ) among these phases may be a

87 written as :

o . d , i ,, >. n = n + n + n (1) 3. oL 3 o.

where n°, n and n^ are the nvmiber of moles of alcohol in a a a

the oil, disperse and at the interfacial region respectively.

Since the solubility of alcohol in the oil phase remains

constant at a particular temperature/ so the dilution of a

microemulsion with oil and further titrating it with alcohol

will still maintain solubility of alcohol constant. Hence

the distribution constant, K, may be written as:

_o K = "a (2)

n o

From equation (1) and (2) we get

n = Kn + n^ + n^ (3) a o a a

Since the moles of alcohol at the interface and in the

dispersed phase depend upon the surfactant concentration,

equation (3) may be converted into a working equation by

dividing both the sides by moles of surfactant in the

66

system i.e. n ,

d i

a = K — ^ + - ^ - i — ^ (4) n n n s s s

n Equation (4) suggests that a plot of —-—— versus

n s — ^ should be a straight line with slope K and intercept s d i <3 4. i

"a "a (say "a "a = I) . Since the s o l u b i l i t y of n n

s s 2-ethyl-l-hexanol is negligible (n^ = 0) in water then I

a.

simply gives the moles of alcohol per mole of surfactant at

the interface. From the slope, K, and intercept, I, of the

straight line plots (Figures 1-3), mole fraction of alcohol

at the interface (X ) and in the continuous phase (X ) a ' a 87

were calculated as ; xi

a

x° a

=

=

I I + l

K K+1

(5)

(6)

The standard free energy change, AG / of t r a n s f e r

for alcohol frcwn continuous o i l phase t o the i n t e r f a c i a l

region were ca lcula ted from the r e l a t i o n :

X^ A G ° = - RT m - I — (7)

67

where T is the experimental temperature. The values of

A G ° at different temperatures, calculated from equation(7), s

are summarized in table 9.

The experimental results presented in tables 7

and 8/ show many interesting features of microemulsion

formation. It is clear from these results that the value

of K remains more or less constant with the oil chain

length in the system. The value of I seems to be greatly

affected by the oil chain length in the system. Value of I

increases with the increase of alkane carbon nxjmber, N , (ACN)

of the oil phase in the system. Higher values of I for

higher alkanes indicate that the alcohol is

preferentially partitioned at the interface for higher

chain length oil. The increased values of X with oil a

chain length in the system also supports the above conclu­

sion.

The temperature effect on microemulsion formation

is of interest. The results in tables 7 and 8 show that

values of I as well as X decrease for both the surfactants a

when the temperature is increased. But no change in the

value of X was observed with the change in temperature.

The variation of X values with tempei'atu/e suggest that a

at higher temperature less alcohol will be needed tc sta­

bilize the interfacial film of surfactant and cosurfactant

68

for the same water pool as the volxime of water in the system Is

kept fixed. The decreased amount of alcohol at the inter­

face i.e. X value further suggests that alcohol solubility a

in the interfacial film is reduced at higher temperature.

Since the amount of alcohol at the interface dictates the 178

water solubilising capacity of the system , the increase

of temperature will play a destructive role when the water

pool of the system will increase. From the figures 1-3 it

can be seen that for the same oil-alcohol combination, alc­

ohol is partitioned more at the interface for MTAB than for

CTAB as reflected in the values of I and X , This observe-

tion suggest that chain length of surfactant also plays an

important role in the distribution of alcohol in different

, 165 phases

The values of standard free energy of transfer of

alcohol from the continuous oil phase to the interfacial the

region (table 9) suggest thaVassociation between emulsi-

fier and cosurfactant (alcohol) increases with the chain

length of oil end decreases with the chain length of emul-

174 sifier . The negetive sign indicete that the process of

microemulsion formetion is spontaneous eno lower values of

/\,G suggest thet there is no requirement of strong intera­

ction between surfactent end cosurfactant molecuJes for

microeinulsification. A comparison of standerd free energy

69

values for CTAB and MTAB in table 9 shows that LG is 3 ess

negative for HTAE containing microemulsion than CTAB. This

indicates that alcohol transference from oil to interfacial

region is favoured by CTAB systems.

Figure 4 shows the effect of water/oil ratio on

the specific resistance of microemulsion systems prepared an

by using different oils and using CTAB as/emulsifier. This

typical electrical resistance behaviour can be explained on

the basis of surface conductance model as suggested by 179 O'Konski for polyelectrolyte systems . According to this

model, the effective volume conductivity can be considered

as the sum of parallel, bulk and surface conductivity con­

tribution. The contribution due to the surface conductivity

is a function of the size of the dispersed particles (water

droplets) and the mobility of ions in the ionic atmosphere

of water droplets. Figure 4 shows that at any n /n ratio

in the microemulsion system the specific resistance increases

with decrease in chain length of oil. This indicates that

the contribution of the surface conductance to the total

vol\me conductance is also reduced by chain length of oil.

In other words it can be attributed due to lower degree of

ionization of surfactant at the interface in presence of

higher chain length oils and to the concomitant thinning of

70

the ionic atmosphere at the interface. In the oil-alcohol

titration study described previously it has been found that i

the value of I i.e. a (Table 7) increases with oil n s

chain length. This increase in "I" value may result in an

increase in the intermolecular distance between surfactant

molecules and thus the surface contribution to the total

conductance will increase leading to a decrease in the spe­

cific resistance. This indeed was observed in figure 4.

From different transitions in figure 4 and also

from visual appearance of microeraulsion systems, it was

observed that when the amount of water was increased in the

system, all the systems pass through clear to bluish to

turbid regions. The bluish region was found to exhibit

birefringence. After birefringence, the system became

opaque, milky and nonbirefringent as the n /n ratio was

gradually increased. The specific resistance in the bluish

region first increases and then falls off rapidly at higher

water content . A possible explanation to this effect may

be the change of water structure possibly from that

of spheres to cylinders to lamellae leading to the phase

separation. Such structural changes in the birefringent

157 region have been suggested on the basis of NMR data

The formation of such structures would decrease the specific

resistance since ions could move through water cylinders or

71

lamellae without passing through the oil/water interfacial

. 165 region

Figures 5 and 6 show the variation of relative

viscosity, , as a function of moles of water per mole of

oil, n /n , in the system. The critical n /n (V ) values o w w o c

at which the microemulsion remains stable have been obtained

at the sharp inflexion points in the 77 versus n /n plots. the

Information regarding/stability of microemulsion droplet and

its size may be obtained from the V values. The V values •* c c

for different oil / isomer of alcohol combination are

shown in table 15, The data indicates that branching in the

cosurfactant produces droplets of larger size and of higher

stability. The branching also enhances the solubilization of

water with the concomitant increase in the water pool size.

Subsequent plots of these V values versus number of carbon

aton6 in the oil chain, N , resulted in straight lines

(Figure 7), From curves in figure 7 it may be seen that the

V values of microemulsion containing a particular oil

(Cj.-C-) increase with the number of carbon atoms in the

alcohol chain. It is also interesting to note that the V

values are lower for normal alcohols than for their iso­

count erpart. These observatioiB led us to conclude that

higher alcohols are partitioned preferentially at the inter­

face than the lower chain ones producing large interfacial

72

178 180 area and concomitant increase in the water pool size '

This water pool is further enhanced if a normal alcohol is rep­

laced by its branched chain isomer. The V values for all c

the alcohols in figure 7 increase with oil chain length.

The V values are always higher for higher alcohols. This

indicates that higher alcohols are preferentially parti­

tioned at the interface producing larger water pool as

observed in our oil-alcohol titration studies reported

earlier^^°.

13

CHAPTgR - H I

KFFECT OP BRINE CONCENTRATION ON THE PHASE BEHAVIOUR

OF SODIUMDODECYLSULFATE/PENTANOLAATER/

BENZENE SYSTEM

74

Microemulsions are thermodynamically stable microstru-

ctured mixtures containing oil, water, surfactant, usually salt,

and often an amphiphilic molecule called a cosurfactant. The

systems forming microemulsions present complex phase bahaviour,

and according to current theory and experiment, the chemical

structure of the cosurfactant plays an important role in such

120 181—183 phase behaviour / • Microemulsions prepared by Schulman,

Rosano and others, where phase diagrams were not extensively

studied actually belong to an isotropic region L^, L^ or an

equilibrium mixture of both, namely the L phase. Different

locations in the L-region may contain different micelles. It

has been found that at any point in this macroscopic "isotropic"

region in the phase diagram there may exist a mixture of micelles

of different shapes and sizes, and in some cases, of different

structures as well ' . Conventional phase diagrams /

however, donot describe metastable states, neglect surface

effects, particularly predominant in small size systems, and

may even omit possible equilibrium phases. Microscopic inh-

omogeneities within the same phase are not always accounted for.

Transformation of one type of micelle to another has been

reported to occur in a single homogeneous region (Supra-

., 130,131 vide)

For a given kind of water/amphiphilic compound(s)/

hydrocarbon system, the larger the microemulsion domain (i.e.,

the range of composition corresponding to the existence of

75

microemulsion-type media), the higher the diversity of mic-

roemulsion structure. This fact is important to the formula-

tor interested in the design of specialty products or of mul-

ticomponent fluids to be used in industrial processes. The

optimum formulation may be obtained by adequately acting on

certain key constitution/or composition parameters of the

system.

Studies on phase equilibria have shown that the sta­

bility of a microemulsion is dependent on the type of surfa­

ctant, on the type of oil, and, in system containing two

amphiphilic compounds; the surfactant/cosurfactant ratio. The

additionof a simple inorganic salt such as sodiumchloride also

strongly affectsthe equilibria. Depending on the surfactant/

cosurfactant used and the amount of salt, the microemulsion

region at a given temperature may either extend continuously

from dilute aqueous solutions to dilute solutions in oil or

divide into oil-rich and water-rich solutions separated by

multiphase regions. Isotropic solution regions which cannot

be diluted continuously with either water or oil are also

184 known . The properties of various phases in the phase

diagram and the effect of sodiumchloride on the properties of

these phases is not completely understood.

In the present study attempts have been made to

identify the possible existence of microstructures in the

isotropic single phase region. The effect of different

76

concentrations of sodiximchloride on the various phases has

also been studied. For this kind of study a typical system;

sodiioindodecylsulfate/water/benzene/n-pentanol was chosen.

First a phase diagram for this particular system was produced

without salt. The water component was then replaced by brine

of different sodiumchloride concentrations. Various phase

diagrams were thus produced and the solution regions of various

phases were then compared. A comparison of areas of various

phases in the phase diagrams would provide information about

the phases in presence of different amounts of sodiumchloride.

To study various microstructures in the isotropic

clear region in the original phase diagram we have chosen a few

points from the solution regions of water rich and water poor

systems. By doing so we were able to collect preliminary

information about the existence of microstructures present

in the various regions of the phase diagram. This existence

was studied by observing the dispersion behaviour of various

phases which were obtained by the variation of brine concentra­

tion in the system. This study has shown that the brine concen­

tration is a sensitive parameter for the stability of multiphase

dispersions. '

Recent investigations indicate that closed aggregates

in oil or water-continuous solutions are formed only when the

volxime fractions of water or oil/ respectively, are low. In

more concentrated systems the solution properties indicate

77 185 that the solutions are best characterized as "bicontinuous"

Various microstructures in the solution region obtained in the

phase diagram of the system (supra-vide) were studied by cond­

uctivity measurements of various systems. These studies provided

an indication of presence of various microstructures character­

ized by the existence of various well defined breaks in the

curves of conductance versus oil/water content. The weight

percentage of various components for the transformation of one

type of microstructure into another, without varying the sur-

factant/cosurfactant ratio which we maintained constant

throughout our study i.e., 0,45 w/w, can be estimated from

these conductivity curves.

78

EXPERIMENTAL

Purification of Surfactant and Solvents:

Sodivundodecylsulfate (SDS) was obtained from BDH

(England). It was purified by repeated crystallization from

ethanol-acetone mixtures and finally extracting from petroleum

ether (60 hours) and chloroform (100 hours). The surfactant

was filtered out and dried in a hot air oven at 50°C, The

purity of the surfactant was checked by microanalysis;

C= 49.73%/ H = 9.02% and S = 11,00%; Calculated value:

C = 49.80%, H = 8.94% and S = 11.02%. The purity was further

ascertained from the absence of minimum in the surface ten­

sion versus logarithm of surfactant concentration plot and

from the determination of its CMC by conductivity method.

n-Pentanol and water were the same as used in Chapter II,

Benzene was a BDH product of high purity grade (99%). Sodium

chloride, an E. Merck (India) product (99%) was used without

further purification.

Determination of Phase Diagram:

Phase behaviour of the system SDS-n-pentanol-water-

benzene with or without sodiumchloride was studied at

25 + 0.1 C by performing at least two experiments for the

same system. First a rough indication of the position of

various phase regions was determined from test tube experiments,

Several overall compositions on a coarse grid in a triangular

73

diagram with the apices water, benzene and surfactant (SDS)

plus n-pentanol mixture were prepared on a weight percentage

basis. The tubes were sealed, shaken and allowed to reach

equilibrium to study the various phases. In the second step

the precise location of the phase boundaries was determined

186 187

by titration . The test tube experiment gave an approxi­

mate information for the selection of appropriate starting

mixture for titration. The titrants used were either benzene

or water or brine solution. In our system equilibrium was

always reached within a few minutes. On reaching equilibrium

all samples show clear phases separated by sharp interfaces.

Special care was taken to ensure that the phase volvimes

remain constant with time. It was found more practical to

start with paste (SDS plus n-pentanol with a constant weight

by weight ratio = 0,45) and benzene and then titrating it

with water/or brine. The titration was performed by taking

1 g SDS and 2.23 g n-pentanol in several glass tubes. To this

paste various amounts of benzene (5 to 90 weight percent) were

mixed. The resulting mixtures were thoroughly mixed with a

glass rod, sealed and then kept in a thermostat at 25°C for

few hours. The coarse mixtures were finally titrated with

water (or brine). Each end point resulted in a traQsition point,

At each transition point the weight percents of all the

components were calculated and plotted on the triangular phase

diagram. The same experiments were repeated by replacing

80

benzene by water or brine and titrating the coarse mixture to

clarity by benzene. Hence by plotting the compositions of each

component corresponding to the transition point would result

in various phase regions in the phase diagram. Phase diagrams

for each concentration of sodiumchloride were produced sepa­

rately.

Conductivity Measurement :

Conductivity measurements of the four component systems

(SDS-n-pentanol-water-benzene) were performed in the clear homo­

geneous region by varying the concentration of water in the

mixture. In another similar set of experiments the conductivity

of solutions was measured by varying the amoxont of benzene in

the four component system. The conductivity measurements were

made by using the same equipment as mentioned in Chapter II,

Any effects of the adsorption of SDS on the inner surface of

the cell and on the electrodes' surface, particularly at low

SDS concentrations/ were avoided by prewashing the cell atleast

twice with the solution under study.

81

RESULTS

A pseudotemary phase diagram obtained for the system:

water-benzene-SDS/n-pentanol (0.45 w/w) is shown in figure 1.

In this figure six major regions could be identified. These

regions are: (i) liquid in contact with precipitated SDS

(S+L), (ii) a clear homogeneous region (L), Ciii) Unstable

emulsion region (E), (iv) a liquid crystalline gel phase (G),

(v) a two phase region, one of the phases, a liquid crystal

and the other a clear liquid (L+G) and (vi) a very narrow

clear region (L') between L+G and E regions. In our study we

assume that L region consists of L^ (water poor) and L^

(water rich) regions.

The effect of sodiumchloride concentration (brine) on

various phase regions is shown in figure 2-4. The phase

volumes of separated phases as a result of various added

brine concentration for some selected overall compositions

(see figure 1; A,B and C) in the K,p region are recorded in

Table 1. Figure 5 shows the separation of various phases as

a fxinction of brine concentration for a selected point 'D'

in the L^_ region.

Various microstructured systems in the clear homo­

geneous L region in figure 1 were identified by conductivity

measurements. No such measurements were made in the narrow

clear region L* . For this study first of all 5,35 and 60

weight percent of benzene and 95, 65 and 40 weight percent

82

of paste (SDS plus n-pentanol), respectively, were taken in

separate flasks and each sample was diluted gradually with

water. The conductivity of mixture, after each addition of

water, was noted. The plots of conductivity versus weight

percent of added water are shown in figure 6. In another

similar set of experiment 20,30 and 35 weight percent of

water and 80, 70 and 65 weight percent of paste (SDS + n-

pentanol), respectively, of the same weight ratio, was

titrated with benzene and the conductivity of the clear

solutions was measured after each addition of benzene. The

conductivity data with weight percent of different components

in the system for both the sets of experiments is tabulated

in tables 2-7. The plots of conductivity versus weight

percent of benzene added are shown in figure 7.

Benzene

83

SDS n - pentanol Water

Figure 1. Ternary phase diagram of the system S D 5 - n -

p e n t a n o l - w a t e r - benzene at s u r f a c t a n t - alcohol

rat io 0-45 ( weight /we igh t )

84 Benzene

SDS / n - p e n t a n o l Brine

Figure 2. Pseudoternary phase diagram of the system S D S - n -pentanol - br ine ( 2-0 weight °/o NaCl ) - benzene

So

Benzene

SDS n -pen tano l Brine

Fig. 3 Pseudoternary phase diagram of the sys tem S D S - n -

p e n t o n o l - b r i n e ( 4 -00 weight "/o NaCl ) - b e n z e n e

86

s*

SDS n-pentanol Brine

Figure 4. Pseudoternary phase diagram of the system S D S - n -pentanol - brine ( 6-0 weight**/© NaCl ) -benzene

87

Table 1: Effect of salinity on the phase volumes, d>, of

separated phases of the system: Ig SDS - 2.23 g

n-pentanol - 10, 30 and 45 weight percent of

benzene and 30, 20 and 15 weight percent of

brine.

NaCl concentration Volume percent Volume percent of of upper phase lower phase

(4>) (4>) (w/w)

A . 9 2 . 2 4 7 . 7 6

B 2%, 9 4 . 4 1 5 .59

C 9 6 . 7 1 3 . 2 8

A 9 1 , 3 5 9 . 6 5

B 6% 9 5 . 7 1 4 . 2 9

C 9 7 . 7 4 2 . 2 6

88

CO]

®

C-053

©

D10 3 D20 3 C-303

(D

C-40D

C-50]

0)

• • • • • • • • • <

• • • • • • • * • •

• • • • •

©

• • • • • •

• • • • • «

• • • • • • • • • • • «

* • • • • a

®

®

®

®

®

®

C10D C2-0] C4-0] C6-03

Increasing brine sal in i ty In the system

®

C12-0J

Fig. 5 Effect of CNaClJ on water r ich microemulsion L WR

of composi t ion : 1 g. SDS - 2-23 g. n - pentonol - 0-58g.

benzene - 19-26 g. br ine component . Values indicated

C D represent ( weight "U ) of sodium chlor ide in

the br ine componen t . ' I ' s tands for I so t rop i c , ' B '

fo r b i re f r l ngen t and ' E * for tu rb id emulsion phases

83

Table 2: Variation of conductance against the weight percent of

components in the system containing 1 g SDS-2.23 g

n-pentanol-0.17 g bsinzene and water at 25 C.

V^eight percent of SDS

25.67

22.76

20.44

18.54

16.97

15.16

14.51

13.53

8.24

7.92

7.84

7.61

7.20

6.72

6.30

5.44

4.28

3.52

3.00

VJeight percent of n-pentanol

57.15

50.65

45.48

41.27

37,78

34.82

32.30

30.12

18.34

17.62

17.44

16.95

16.04

14.96

14.01

12.11

9.52

7.85

6.67

Weight percent of water

12.82

22.73

30.61

37.04

42.37

46.88

50.72

54.05

72.02

73.12

73.39

74.14

75.54

77.18

78.62

81.52

85.47

88.03

89.82

Weight percent of Benzene

4.36

3.86

3.47

3.15

2.88

2.65

2.47

2.30

1.40

1.35

1.33

1.30

1.22

1.14 •

1.09

0.93

0.73

0.60

0.51

Conductance

(ohm~ )

1.11x10"^

2.86x10"-^

5.00x10"^

6.25xl0'"-

6.67xl0~^

7.14x10"-^

7.14x10"^

7.14x10"^

6.07x10"^

6.67x10"^

7.14x10"^

8.33x10"-^

9.09x10'^

9.09x10"^

9.09x10"^

8.33x10"^

7.14x10'^

6.67x10'-^

6.25x10'^

90

Table 3: Variation of conductance against the weight percent of

components in the system containing 1 g SDS-2,2 3 g

n-oentanol-1.74 g benzene and water at 25°C.

Weight percent of SDS

18.48

17.51

16.63

15.97

15.48

14.90

14.37

13.87

13.40

12.97

12.56

12.18

6.18

6.08

6.01

5.90

5.82

5.74

4.78

4.56

4.01

. 3.03

2.R6

Weight percent of n-pentanol

41.12

38.96

37.03

35.55

34.45

33.17

31.98

30.87

29.84

28.80

27.97

27.11

13.75

13.54

13.38

13.13

12.92 •

12.76

10.63

10.14

8.93

6.74

6.38

V7eight percent of water

8.30

13.11

17.44

20.73

23.18

26.04

28.69

31.16

33.47

35.62

37.64

39.54

69.35

69.82

70.20

70.71

71.14

71.55

76.30

77.38

80.10

84.97

85.79

Weight percent of Benzene

32.10

30.42

28.90

27.75

26.89

25.89

24.96

24.10

23.29

22.53

21.83

21.17

10,73

10.56

10.41

10.26

10.10

9.95

8.29

7.92

6.96

5.26

4.97

Conductance

(ohm'-'-)

9.09x10"^

18.51x10"^

2.81xl0~*

3.74x10"^^

4.67x10"^

6.06x10""^

8.13x10""^

1.00x10"-^

1.36x10"^

1.75x10"^

2.32x10"-^

2.70x10'^

9.52x10*^

9.52x10"^

9.09x10'-^

9.09x10"^

8.33x10"-^

8.33x10'-^

8.33x10"^

7.69x10"^

7.69xl0~-^

6.25x10"^

5.88x10"-^

91

Table 4: Variation of conductance against the weight percent of

components in the system containing 1 g SDS-2,23 g

n-pentanol-4,85 g benzene and water at 25°C.

Weight Weight weight percent of percent of percent of SDS n-pentanol water

weight Conductance percent of _. Benzene (ohm~ )

12 .02

1 1 . 6 8

1 1 . 3 7

1 1 . 0 3

1 0 . 7 3

10 .45

10 .19

9 . 9 3

9 . 6 9

9 . 4 6

9 . 2 5

9 .04

8 .84

8 i 6 5

6 .92

6 . 8 7

6 .75

2 6 . 7 6

2 6 . 0 0

2 5 . 3 0

24 .54

2 3 . 8 9

2 3 . 2 7

2 2 . 6 8

2 2 . 1 1

2 1 . 5 8

2 1 . 0 7

2 0 . 5 8

2 0 . 1 1

1 9 . 6 7

1 7 . 0 1

1 5 . 3 9

1 5 . 2 8

1 5 . 0 3

3 . 0 0

5 . 8 0

8 . 4 0

1 1 . 0 1

1 3 . 3 9

1 5 . 6 5

1 7 . 8 0

1 9 . 84

2 1 . 7 8

2 3 . 6 3

2 5 . 3 9

2 7 . 0 8

2 8 . 6 8

3 0 . 2 2

4 4 . 2 0

4 4 . 5 8

4 5 . 5 2

5 8 . 2 2

5 6 . 5 2

5 4 . 9 3

5 3 . 4 2

5 1 . 9 8

5 0 . 6 2

4 9 . 3 3

4 8 . 1 2

4 6 . 9 5

4 5 . 8 4

4 4 . 7 8

4 3 . 7 7

4 2 . 8 1

4 1 . 8 9

3 3 . 4 9

3 3 . 2 7

3 2 . 7 0

2 . 7 0 x 1 0 " ^

8 . 3 3 x 1 0 " ^

1 .36x10~^

1 .67x10"^

1 . 9 4 x 1 0 ' ^

2 . 4 2 x 1 0 " ^

3 . 7 0 x 1 0 " ^

9 . 0 9 x 1 0 " ^

3.63x10*"^

l . l l x l O " - ^

2 . 2 7 x 1 0 " ^

2 . 0 0 x 1 0 " ^

2 . 1 7 x 1 0 " ^

7 . 6 9 x 1 0 ' ^

12.50xl0~-^

1 4 . 2 9 x 1 0 " ^

1 1 . 1 1 x 1 0 " ^

92

E £. O

o c o • J

o c o o

95

90

0

Hetrogeneous system

( Wt »/o of benzene )

20 100 AO 60 80

Weight percentage of water

Fig. 6 Variation of electrical conductance with weight percent of water in the system : 1g SDS - 2'23g. n - pentanol and various in i t ia l fixed compositions of benzene

93

Table 5: Variation of conductance against the weight percent of

components in the system containing 1 g SDS-2.23g

n-pentanol-0,81 g water and benzene at 25 C

Weight percent of SDS

24.80

23.52

22.36

21.32

20.36

19.49

18.69

17.95

17.27

16.64

16.05

14.99

14.07

13.25

12.52

11.87

11.27

10.74

10.26

9.82

9.41

9.04

8.37

7.80

7.18

6.76

Weight percent of n-pentanol

55.20

52.35

49.78

47.44

45.32

43.38

41.60

39.96

38.44

37.04

35.73

33.38

31.31

29.49

27.87

26.41

25.09

23.91

22.84

21.85

20.95

20.11

18.64

17.36

15.99

15.04

Weight percent of water

20.00

18.97

18.03

17.19

16.42

15.71

15.07

14.48

13.93

13.42

12.95

12.09

11.34

10.68

10.10

9.57

9.10

8.67

8.28

7.92

7.59

7.29

6.75

6.29

5.79

5.45

Weight percent of Benzene

0

5.17

9.83

14.05

17.90

21.41

24.64

27.61

30.36

32.89

35.27

39.53

43.27

46.58

49.51

52.15

54,52

56.67

58.62

60.41

62.04

63.55

66.23

68.55

71.03

72.75

Conductance

(ohm. )-i

2.7x10"-^

1.89x10'-^

1.27xl07^

8.77x10"*

5.99x10"*

4.25x10"*

3.01x10"*

2.35x10"*

1.67x10"*

1.26x10"*

1.00x10"*

6.25x10"^

4.08x10"^

2.90x10"^

2.11x10"^

1.60x10"^

1.27x10"^

1.02x10"^

7.14x10"^

6.45x10"^

5.26x10"^

5.00x10"^

4.08x10"^

3.23x10"^

2.67x10"^

2.38x10'^

94

Table 6: Variation of conductance against the weight percent of

components in the system containing 1 g SDS-2,23 g

n-pc-ntanol-1.38 g Water and benzene at 25 C.

Weight percent of SDS

21.70

20.71

19.81

18.90

18.22

17.52

16.87

16.27

15.71

15.18

14.69

14.23

13.80

13.01

12.31

11.68

11.11

10.12

9.29

8.59

7.99

7.46

7.23

Weight percent of n-pentanol

48.30

46.09

44.09

42.08

40.56

39.00

37.55

36.21

34.96

33.80

32.71

31.68

30.72

28.97

27.39

26.00

24.72

22.52

20.69

19.12

17.78

16.62

16.08

Weight percent of Water

30

28.64

27.40

26.15

25.20

24.23

23.34

22.50

21.72

21.00

20.32

19.69

19.09

. 18.00

17.03

16.15

15.36

14.00

12.85

11.82

11.05

10.32

10.00

Weight percent of Benzene

00.00

4.50

8.70

12.88

16.01

19.24

22.24

25.02

27.60

30.02

32.28

34.40

36.39

40.02

43.27

46.18

48.89

53.35

57.17

60.40

63.18

65.60

66.69

Conductance

(ohm*^)

6.67x10"^

4.44x10"^

2.98x10"-'

1.96x10'-'

1.39x10'-'

8.93x10"*

5.65x10"*

3.95x10"*

2.86x10"*

2.08x10"*

1.53x10"*

1.16x10"'^

9,09x10"*^

5.71x10'^

3.97x10"^

2.81x10'^

2.12x10"^

1.32x10'^

9.52x10'^

7.14x10"^

5.71x10"^

5.13x10'^

5.00x10'^

95

Table 7: Variation of conductance against the weight percent of

components in the system containing 1 g SDS-2.23 g

n-pentanol-1.74 g Water and benzene at 25 C.

Weight percent of SDS

20.15

19.29

18.51

17.78

17.11

16.49

15.92

15.38

14.88

14.41

13.97

13.16

12.79

12.44

12.11

11.81

11.49

11.22

10.94

10.69

10.21

9.77

9.37

9.00

8.66

8.34

8.04

7.77

7.51

7.27

Weight percent of n-Pentanol

44.85

42.94

41.19

39.58

38.09

36.72

35.43

34.24

33.11

32.06

31.08

29.28

28.46

27.68

26.95

26.28

25.59

24.97

24.36

23.78

22.72

21.73

20.84

20.02

19.26

18.55

17.90

17.29

16.72

16.19

Weight percent of Water

35.00

33.52

32.16

30.91

29.74

28.67

27.66

26.73

25.85

25.04

24.27

22.86

22.22

21.61

21.04

20.45

19.98

19.48

19,02

18.57

17.74

16.98

16.28

15.63

15.04

14.49

13.98

13.50

13.05

12.64

Weight percent of Benzene

0

4.24

8.13

11.72

15.04

18.12

20.99

23.66

26.15

28.49

30.68

34.69

36.53

38.26

39.90

41.46

42.94

44.34

45.68

46.96

49.34

51.51

53.51

55.35

57.04

58.62

60.08

61.44

62.72

63.91

Conductance

(ohm"^)

7.87x10"-^

5.62x10"-^

3.94x10"-^

2.67x10"^

1.85x10"-^

1.28x10'-^

8.93x10"'*

5.25x10"*

4.48x10"*

3.29x10"*

2.33x10"*

1.39x10"*

1.11x10"*

9.09x10*^

7.69x10"^

5,85x10"^

4.90x10"^

4.27x10'^

3.70x10"^

3.28x10"^

2.47x10"^

2.00x10"^

1.67x10"^

1.48x10"^

1.33x10"^

1.2 0x10"^

1.16x10"^

1.13x10"^

1.17x10"^

1.17x10"^

9o

Wt "/o of water

a —• » - 20«/o

b -^ A— 30 "/o

Weight percent of benzene >-

Figure 7 . Var ia t ion of e lec t r ica l conductance wi'th weight

percent of benzene in the s y s t e m : l g S D S - 2 ' 2 3 g

n -Pen tano l and var ious Init ial f ixed weight percent

of water

97 DISCUSSION

In order to visualize important trends in phase beha­

viour and to pictorially represent various phase regions on

a triangular graph paper, it was necessary to group two

123 components together and treat them as a pseudocomponent

In this way dimensionality of the system could be reduced for

practical purpose though such reduction always involves loss

of details of phase behaviour to some extent. In the present

study we have treated surfactant plus cosurfactant and sodium-

chloride plus water as pseudocomponents. In our study brine

was found a suitable pseudocomponent.

The change in nature and characteristics of various

phases with the composition of various components is shown in

figure 1, The phase boundary between single phase L and the

phase S+L, comprising a liquid in contact with precipitated

SDS, was obtained by observing precipitate formation. The

overall chosen compositions were restricted to S+L region.

The precipitate in S+L region dissolved when the temperature

was increased. The test tube was then shaken and allowed to

cool to 25®C, If any precipitation of SDS occured at 25°C a

small amount of water was added to dissolve the precipitate.

The procedure was repeated untill no precipitation was found

at 25°C. This method has been shown to be more accurate than

the determination of this phase boundary starting from single

phase region in which precipitation of SDS in the latter stages

results in inaccuracy.

98

A perusal of the boundary line between phases S+L

and L in figure 1 shows that when the composition of benzene

in the system is increased a clear region is obtained at a

very low weight percent of water. The solution region also

decreases with the increase in the oil content in the

system . This behaviour could be explained on the basis of

the fact that n-pentanol, owing to its solubility character­

istics, transfers from the micellar phase to the continuous

oil phase. Such transfer of alcohol decreases the amount of

interfacial alcohol necessary to produce large interfacial

area. This reduced interfacial area results in small pool

size of water droplet and hence the concomitant decrease of

157 water content at higher oil content . Figure 1 shows that

microemulsion's three dimensional domain consists of three

disjoined volumes namely Lyjp/ l^^ and a narrow L', which

188 indicate that the system under study is a type S system .

Owing to the discontinuity existing between water rich and

water poor L regions of microemulsion domain, it may be

predicted that microemulsion structure varies greatly with

the composition of various components in the system. The

possible existence of various structures in different regions

of the microemulsion domain (L) will be discussed on the

basis of the electreconductive behaviour of the entire micro-

emulsion system in that domain.

93

Initially by starting with a fixed surfactant/cosurfact-

ant ratio and upto a maximum of 10 weight percent of benzene,

a gradual addition of water leads L-region to transfer to

L+G region which changes to a G region and finally to another

clear L region. This gradual transition of phases indicates

that G region is flanked by two regions corresponding to the

existence of either L^+G or G+L. diphasic media, where L.

and L» may be defined as direct and reverse microemulsion

systems respectively. Thus it clearly appears that the transfer

of L_+G through G to G+L^ defines a range of composition over

which the microemulsion phase inversion occurs. This observa­

tion is consistent with one of the possible phase inversion

71 processes listed in Winsor's scheme

Phase transitions from L region through emulsion,

L+G, L' and finally to an emulsion region were observed by

gradually adding water to the system in the Il,p region

containing benzene slightly higher than 10 weight percent.

In the L .p region near the benzene apex, various visual

transformations were observed by adding small amoxints of

water in the system. The system's appearance changed from

clear to bluish to turbid. These visual transformations may

be due to the change in water structure from spherical to

lamellar to hexagonally close packed water cylinders as

reported in the past 1' ° ' , A small lenticular area L'

appearing between the emulsion region and L+G region defines

100

a narrow composition range over which the system's phase

behaviour seems highly complex. We are not in a position to

discuss the nature of microemulsion and structure of aggre­

gates existing in this region. However, such microemulsion

175 189 regions have been reported in the past ' , On the basis

of conductivity data it has been reported that these peculiar

microemulsions are water-continuous media. They however

cannot be classical "direct" microemulsions, because their

benzene content generally exceeds that corresponding to

190 the random close packing and even the face-centered

191 cubic close packing of identical hard spheres . This

implies that they possess an "exotic" structure of the

bicontinuous sort. Since in L' region microemulsion compo­

sitions are highly xinbalanced in favour of benzene, it may

be wondered whether these microemulsions are bicontinuous

in the usual sense, which is more suited to microemulsions

192 containing water and hydrocarbon in comparable amounts

A possible alternative model for the structure of L'micro­

emulsions would be that of a dynamic random arrangement of

organic polyhedral microdomains separated by thin aqueous

193 films. This model, envisaged by Lissant to depict

emulsions whose disperse phase content is very high, also

194 has been used by Chen et al, to explain the apparently

anomalous electroconductive and viscous behavior of water-

poor three component microemulsions incorporating didode-

cyldimethylammoniumbromide as ionic surfactant and no cosur-

factant.

101

The effect of salinity on the phase behaviour of four

component systems is shown in figures 2-4, When the salinity

in the system is increased all the mesomorphous phases,

water rich L-region, lenticular clear region L' and the

water poor L-region either disappeared or are strongly

reduced with respect to the one obtained with pure water

(see figure 1) , The phase boundary between It.p and S+L

regions also moves slightly in the direction of the brine

apex with increasing salinity because addition of sodium-

chloride causes precipitation of SDS (salting out effect).

The progressive decrease in the area of L^„ region

at the brine apex and shrinking of L„p with the progressive

increase of salinity in brine phase may be due to the dec-

reased solubility of water in the microemulsion phase ' J»I i

The addition of small concentration of salt into the micellar

solution have been reported to increase the micellar size and

195 oil solubility in the system , This means that the increased

solubility of oil makes the microemulsion droplets/micelles

more compact in presence of salt and excludes water out of

142 the microdroplets

In our study increase in salinity produces a biphasic

system with the upper phase being a surfactant plus pentanol

rich microemulsion and the lower presvimably a surfactant poor

aqueous salt solution. The existence of various microstructures

was initially checked in the homogeneous single phase, L^JP*

102

region at various compositions say at 'A', 'B' and 'C of

the system (see figure 1) in presence of 2 and 6 weight

percent of brine solution. The calculated values of phase

volumes, 0, of the separated phases are listed in table 1.

It may be seen from table 1 that the phase vol\ime of

upper phase at 'A' decreases while that of lower increases

with increasing salinity. Contrary to this, the phase volvunes

of upper and lower phases at *B' and 'C show a reverse

trend. To qualitatively check the nature of the emulsion in

the phases a drop of upper phase of solution 'A' was put in

pentanol and water in separate beakers. The drop was found

to be immediately dissolved in pentanol but spread in water.

For solution 'B', the drop was slowly dispersed in pentanol

but formed an upper layer in water which dispersed after

sometime. For solution 'C' the drop was settled at the bottom

in pentanol and then dispersed slowly while in water it formed

a white emulsion which slowly dispersed in water resulting in

a clear solution. Putting a drop of solutions 'A', 'B' and

'C in benzene resulted in an immediate precipitation of

surfactant. From these visual observations it may be concluded

that depending upon the composition of the system there exist

different microemulsion zones in the clear homogeneous LL._

region.

The effect of salt concentration in extracting water

from the homogeneous phase is more pronounced in the surfactant/

103

cosurfactant rich region, where lamellar structures are expected

to exist. The water extracting effect seems less pronounced in

oil rich regions. However, a reverse effect of water solubility

is noticed (see table 1) by increasing salinity from 2 to 6

weight percent. This observation is consistent with the

195 reported effect in the literature . It is interesting to

note that the addition of different concentrations of sodium

chloride into the brine phase destabilizes a typical o/w t

microemulsion system in the L^^ region to various extent.

Figure 5 illustrates the formation of such phases for a typical

microemulsion system comprising Ig SDS, 2,23 g n-pentanol,

0,58 g benzene and 19.26 g. aqueous phase (see figure 1,

point D). It can be seen from figure 5 that the addition of

just 0,05 weight percent of aqueous salt solution results in

breaking of the microemulsion into a two phase systera, upper

phase being a diffused system. When the amo\int of sodium-

chloride in aqueous phase was increased to 0,1 weight percent

the volume of upper emulsion phase increased. Further increa­

sing salt concentration upto 0.3 weight percent changed the

entire system to a very stable emulsion system. The emulsion

remained stable and no phase separation took place even after

keeping it for more than a month's time. When the percentage

of sodiiimchloride was increased to 0.4 weight percent the

system separated into an upper emulsion phase and a clear

lower phase. Two clear phases with distinct boundaries were

obtained when the salinity was increased to 0,5 weight percent

104

the upper phase was of smaller volume than the lower aqueous

phase with a bluish tinge. But when the concentration of sodixim-

chloride was raised to 1,0 weight percent the vol\iine of upper

phase increased and the colour of lower phase became more

bluish. The volume of upper phase further increased when the

salinity was 2.0 weight percent. Further addition of salt into

aqueous phase upto 12 wegith percent didnot cause any appre­

ciable change in the volvmies of upper and the lower phases.

The nature of inversion from w/o to o/w microemulsion

is quite controversial. An abrupt inversion, a phase separa­

tion, or a gradual change through bicontinuous structures has

been proposed ' ' ' , Attempt has been made to study

such changes by measuring the conductance of the system as a

fxinction of water/or oil content. Figure 6 shows the variation

of electrical conductance as a function of water content in

the system. Solid and dotted part of the curves represent

homogeneous and heterogeneous systems respectively. The initial

amount of benzene for three different sets of systems was

kept 5,35 and 60 weight percent. Various amounts of water

were then added. Prom figure 6, curve a, it could be seen

that the conductivity first rises and then falls off rapidly

with the added water in the L and LL^ regions respectively.

The conductivity of the system (see figure 6, curve b), with

35 weight percent of benzene, initially rises slowly and later

on shows a similar trend to that of curve 'a'. When the com­

position of benzene is raised to 60 weight percent the

105

conductivity first remains almost constant upto about 18 weight

percent of water (see curve 'C') and then rises steeply with

the further addition of water in the system.

Curve 'a' (figure 6) shows a typical conductivity

behaviour of the system with low oil content which changes

with the addition of water. The conductivity rises and the

system remains clear upto about 50 weight percent of water.

Right from the beginning i,e,, 10 weight percent water and

5 weight percent of benzene the system is neither . oil

continuous nor water continuous. This microeraulsion may be

called a water-in-oil like microemulsion in which alcohol

and oil due to their mutual solubility form a continuous

phase and the water is solubilized in it. Further addition

of water upto 75 weight percent results in an emulsion

formation. The system inverts from an emulsion to an oil-in-

water microemulsion which may be characterized from its

conductivity behaviour which falls of rapidly on dilution

with water.

When the initial percentage of benzene in the system

was increased from 5 to 35 weight percent, the water-in-oil

like microemulsion showed a slightly different conductivity

behaviour. The phase separation and inversion from emulsion

to oil-in-water microemulsion also occured at 40 and 80

weight percent of water. However, when the composition of

benzene was kept 60 weight percent, no inversion to oil-in-

106

water microemulsion was observed (Curve 'c*). No change in

conductivity of the system was noticed upto 18 weight percent

of water showing a typical behaviour of a water-in-oil

microemulsion. Further addition of water upto about 27 weight

percent of water shows the behaviour of water-in-oil like

microemulsion. In this case the only possible observable inver.*

sions were from water-in-oil to water-in-oil like micro­

emulsion to an emulsion region. Prom these results it may

be concluded that the inversion from w/o to o/w microemulsion

does not take place abruptly but through some possible bicon-

tinuous structures. The conductivity results for these

experiments are tabulated in tables 2-4,

The existence of various microstructures in the clear

LL region was identified from the conductance measurements

as a function of added benzene and fixed the amoiont of SDS

and n-pentanol. The initial amoiint of water for three

different sets of systems in this region was kept at 20, 30

and 35 weight percent. Various amounts of oil were then

added in each system in such a manner that the composition

of the systems remain within the L^- region. The measured

conductivity results for this set of experiments are tabulated

in tables 5-7 and shown in figure 7, From figure 7 (curves

'a', 'b' and *c'), it is demonstrated that the clear homo­

geneous L^p is not an isotropic one. Existence of discontinuities

in the plots indicate the presence of various microstructures

107

at different composition of the components. At low water

content (20 weight percent) and high concentration of SDS

and n-pentanol the system is highly conducting (see figure 7,

curve 'a'). The system's conductivity increases sharply

when the initial concentration of water is increased by 30

and 35 weight percent (Figure 1, curves 'b* and 'c'). This

typical conductivity behaviour at high "SDS/n-pentanol"

concentration shows the existence of lamellar structures in

197 this region as suggested by other workers . The conductivity

of the system decreases gradually by the addition of benzene

resulting in sharp breaks at 11, 17 and 20 weight percent of

benzene. Depending upon the initial amount of water and

gradually increasing benzene contents in the systems results

in sharp breaks in the conductivity curves. The microemulsion

regions under successive break points in the conductivity

cur-ves indicate that there exist different microstructural

droplets in the clear homogeneous L^p region which may be

w/o, o/w or w/oil-like microemulsion with mixed spherical

198 and lamellar structures as proposed for similar systems .

103

CHAPTER « IV

IMFLUBNq; OF ALlOfL CHAIN BRANCHING OF COSXJRFACTANTS

ON THE S0LUBILI2ING CAPACITY AND THE STRUCTXJRE

Qg MICROEMULSION SYSTEMS

103

Many different combinations of surfactants, nonpolar

solvents, 'and water form microemulsions. Among the most

extensively studied systems are those containing an ionic

surfactant, a medium chain length alcohol as cosurfactant,

water, a hydrocarbon and salt. Microemulsions without cosur­

factant and some with long chain amines are becoming more

popular these days, Microemulsions typically require 6 to 8

and 8 to 14 percent by weight of surfactant and cosurfactant

199 respectively . It was observed that as the hydrocarbon level

goes above 50% (w/w) of the ccxnponents other than water, the

ability of a microemulsion to solubilize water decreases

sharply • This limits the ability to dilute a microemulsion

system with the hydrocarbon or to add large amotmts of

water. This is a major limitation on the application of mic­

roemulsion technology in diluting w/o microemulsion systems

with water or oil. Another problem is to increase the mutual

solubility between a polar and a nonpolar liquid for example,

water and "oil" by adding an appropriate amphiphile (or a

mixture of amphiphiles) in order to prepare a homogeneous

liquid mixture with as little amphiphile as possible.

Although almost every component influences the various

physicochemical propejrties of a microemulsion but the chain

lengths of alcohol, oil and surfactants have been reported to

drastically influence these properties'^®'^^^'^^^'^''®'^°°.

Greatly enhanced water solubilizing ability is observed at

110

high hydrocarbon levels when quarternary ammonium salts are

used in place of more common anionic surfactants. From the

survey of literature it was found that in the preparation of

microemulsions generally normal alcohols and n-alkanes have

been extensively used. But no attempts seem to have been made

to prepare a range of microemulsions by using various isomers

of alcohols such as their branched chain counterparts and then

to study their effect on water solubilizing limit of micro­

emulsions.

In the present chapter the water solubilizing capacity

of water-in-oil (w/o) microemulsions comprising of sodium salts

of fatty acid soaps (Cj .-Cj g)-isomers of alcohols (C.-Cg)-

n-alkane (€^"0^)t have been investigated at 30°c, Water solu­

bilizing capacity of soap microemulsions was compared with

those formed by using Cetyltrimethylammoniximbromide (CTAB) and

sodiumdodecylsulfate (SDS) surfactants as emulsifiers. The

interfacial compositions of microemulsions were determined by

oil-alcohol titration method as described earlier. The elec­

trical resistance measurements of microemulsion systems have

also been performed as a fionction of alkyl chain length of

oil and the nature of alcohol. These studies were carried out

with the view to qualitatively estimate the degree of ioni­

zation of soap molecules (thickness of ionic atmosphere around

the droplet) and its dependence on the oil, surfactant and

alcohol alkyl chain length.

I l l

EXPERIMENTAL

Chemicals and Solvents :

Sodixim salts of long chain saturated fatty acids

(C-., C,^ and CIQ) were prepared by mixing eguimolar quan-14 ID lo

tities of an alcoholic solution of the fatty acid and sodium

hydroxide followed by refluxing the mixture for about eighteen

hours. The soap was filtered \inder vacu\iro and crystallized 2

repeatedly from ethanol-water mixture • The fatty acid soaps

thus prepared were dried in a vacuum oven at constant tem­

perature (40°C), The purity of each soap was ascertained by

CMC measurement by conductance or surface tension methods.

The CMC values of soaps in water were found consistent with

201 the literature values . CTAB, SDS, water, n-pentane, n-hexane,

n-heptane, 2-ethyl-l-hexanol (iso-octyl alcohol) iso-pentanol

and n-pentanol were the same as used in the earlier work.

Isobutyl alcohol, n-butanol and n-nonane were B.D.H. products

of high purity grade (99%). All the solvents were used as

supplied unless stated otherwise.

Determination of Water Soliibilizing Capacity of Microemulsion

Systemsi

First of all the influence of branching in the cosur-

factant chain on water solubilizing capacity of microemulsion

systems composed of various emulsifiers, viz., sodivun stearate,

sodium pa Imitate, sodium myristate, CTAB and SDS, cosurfactants.

112

viz., n-pentanol, iso-pentanol/ n-butanol, iso-butanol, n-

octanol and iso-octanol, and oils, viz., n-pentane, n-hexane,

n-heptane and n-nonane has been investigated, A typical mic-

roeraulsion system was prepared by mixing 1 g of fatty acid

soap, 8 ml of isomer of alcohol, 10 ml of oil and 1 ml of

water. The mixture(s) thus obtained were clear. The samples

were immersed in a constant temperature water bath maintained

at 30 + 0,1°C. After reaching thermal equilibrium water solu-

bilizing capacity of the system was determined by adding water

from a graduated pipette xintil turbidity ccxranenced and the

system separated into two distinct phases. The appearance of

turbidity and the separation of phases was taken as the end

point. In most of the cases the end point was very sharp

(within + 0,02 ml of added water). In few cases the end points

were initially not shai P (slight turbidity) but became clear,

and the systems separated into two distinct phases, after

standing for a few minutes. In a similar set of experiment 2 g

of sodium stearate was used instead of 1 g of sodium stearate

in order to observe the effect of concentration of emulsifier

at the interface on water solubilizing capacity of the micro-

emulsion system. The water solubilizing capacities of microe~

mulsions prepared by using ionic surfactants such as SDS and

CTAB were compared with soap microemulsions. It was found that

like soaps, microemulsion formation was not possible with 8 ml

of cosurfactant when ionic detergents were used as emulsifers.

113

Hence 5 ml of cosurfactant was used to prepare microemulsion

system with these detergents.

Determination of Interfacial Parameters of Microemulsion

Systems:

The method of preparation of microemulsion systems

was the same as described in chapter II. At constant tempera­

ture (30°C), a microemulsion was initially produced by mixing

1 g of emulsifler« 3 g water, 10 ml of oil and finally titra­

ting the coarse mixture with pentanol to obtain a clear solu­

tion. More oil was then added which turned the system turbid.

The turbid mixtute was titrated with the cosurfactant until

it became transparent again. This process was repeated by

adding oil and titrating with alcohol to obtain several experi-

mental points . From this oil-alcohol titration data the

interfacial parameters were determined by the same method as

described in chapter II.

Electrical Resistance Measurements t

The effect of branching in the cosurfactant chain and

the effect of chain length of oil and emulsifier on the* degree

of ionization of soap molecules in the microemulsion system

was determined by electrical resistance measurement study. For

this study microemulsions were produced by mixing 1 g of soap,

10 ml of oil, 8 ml of pentanol and an apropriate amount of

114

water necessary to get a clear solution. The electrical resis­

tance of the system was measured by gradually diluting with

water until turbidity commenced. The critical volume of

alcohol necessary to saturate the interface was determined by

electrical resistance measurement as a function of amount of

added alcohol in the system while keeping other components

constant.

115

RESULTS

The water solubilizinCf capacities of microemulsions con­

taining 1 g fatty acid soap are given in table 1, Table 2 shows

the water solubilizing capacities of microemulsions prepared by

using 2 g of sodium stearate. The experimental data for

water solubilizing capacities of different SDS and CTAB micro­

emulsions is given in table 3. The oil/alcohol titration data

for sodium myristate, sodium palmitate and sodium myristate

microemulsions are tabulated in tables 4-6, The plots of nxomber

of moles of alcohol per mole of soap, n /n , versus number of a s

moles of oil P®^ mole of soap , n^/ng, for different soaps,

oils and isomers of pentanol are shown in figures 1-3, From the

slope (K = nf/n^) and intercept (I = n^/n„) of these straight

line plots the mole fraction of alcohol at the interface (X^) a

and in the continuous oil phase (X° ) have been calculated as described in Chapter II, The values of the standard free energy change, Z\ G°, for the transfer of alcohol from the continuous s

oil phase to the interfacial region were also calculated. The

values of xf, X°, I, K and A G ° for different microemulsion

systems are summarized in tables 7-9. Figure 4 (a,b and c)

shows the variation of A G ° with the alkane carbon number (ACN), s

n , in the alkyl chain of oil. c

The variation of electrical resistance with the water/oil

ratio in different soap microemulsion systems is shown in

figures 5-7 and the data is tabulated in tables 10-12. The

variation of electrical resistance as a fxinction of araovmt of

added alcohol in the sodium stearate microemulsions is shown in

figure 8 and the experimental data is given in table 13.

c o (0

r-t

e 0) o u • o u

•H O

e o CO

O +) C «J m >: '--

c ^ 0)

u

u c (0

u JQ •o c

•S

o c o

•H O (Q

Wi 0) +> (d

0)

r-t

«

O • c

CO

u 0) •p

g X

rH (0 + c c o

•p (d N

r^ •

•<

a. (d o n

en

o

0) n o

I

0)

(0 •H

0 to

0) +> m

<d

o CO

(U +j to M Id

(0

O CO

o U I o (0 H

ac o u I c X o

vo u I o (0 H

X

o in

u

o u I o (Q

o o I C3

s o

in O I O (0 H

X o

in O I c X o I o 0} H

X o

•<» u i c X o I o n

X o

in

G

J? 1

O

O VO

00

in

CO

vo

o

in

i n

o CM

in

00

ro

in

00

CO VO

vo

ro

5C

s 04

CM

o

vo

in o

vo

c^

vo

o in

o

vo

in

vo CO

in.

ro

vo CM

• VO

o

00

0)

0) s I c

vo

00 CM

O CO

O

in

CM CM

CM CO

in

CO

o

vo

VO

o

vo »-l

• vo

CO

CO vo

c (d

P I « I e

o

ro

00

o

o CO

i n

o c

00

CM CTi

CO

vo

00

vo

CM ON

vo

00 ON

• ro

CO O

• VO

in CO

in

in

in

a> c (d a o I e

l l o

o o 0) O

0) o u o

o c (0 X <0

<0

u •o «>

u c 2 A c

i o c

O

§

N

fX

o CO

u «

IS

0) f - l

(0

CO I

DM

(U

c

I c

PH

2 (0 0)

o CO

D»

CM

«U

o •o o (0 o p< i

u o o n

+>

<0

0) •p 10 •X

c <0 E

o

E

c o •rl •P (0 N

o 0)

0) •P (0

0)

c (0 c 0 s 1 c

CM CTi •

(Ti

vD n •

<yi

in r-\

• '3* «-l

ID

r~ • o r-\

n ro +»

0)

c 10 X 0) X I

c

0) c (0 •p c 0)

I

117

o ,c o u

o m •

ON

CM •sJ" « 00

in

r-• in

in •t

• o

in

o • a\

in CM • 00

in tH

• VO

o r-^

• O

in in • 00

M* VO • r-

o 00 •

<j>

• in • o

•H o c (0 •p B 0) (X 1 c

0

c (0 +> c 0) a 1 0 0) H

r^ 0 c (0 +J 3 m 1 c

iH 0 c ro •P ;J CQ i 0 « H

c 0

•H (0

rH 3 E 0) 0 M U

•H E

i H

0 c JS

rH (0

c •H 10 X u •0 0) X o c (0 u A

-o B (0

T-i to

g 0 c «H 0

•P •H E •H •-H

C 0

•H •P (d N

•H i H •H / I 3 •H 0 m u 0) 4J (0 2

• U

0 o <n •P (d

•P

§

10 tM M 3 CO 0 u

i H

E in 1 u 0) +) 10 » 1 0) c 10 X r H (0

i H

<§ rH 1

^ - N

X •H P

N—^

•P c (0 +> o rO %t U P CO

b t H

M-l 0

•d 0)

m

0) rH

rt) EH

CO O a, e o o (Q E 0) •P CO > 1 (0

CO Q (0

n 00

H O >

00 c

I

c s o «n - -o

m

0)

c (0 X rH

T

§ in o

I a

o u I o CO

H

X o o I c

X o

CO o i o to H X o

00 o I c X o

in o ^ I <-H 0 E to ^

H

X

o ^ in r-i

U E 1 *-' c a: o O rH (0

O n* ^ E

U - ' I

c

CO rH

00

0%

<M

CO CO

E

CO CM

•

in in

in

in crv

in

in

0) c (0

c cu I c

CO

CM

CM

CM

CM

in

in in

00

CO

in

in

118

00 Ov

in CM

in

CM

O

O 00

• CM

in

in

o rH in

CM

in

in

(U c (0 X d) X 1 c

<u c (0 p P4 0) a: 1 c

0) JZ +J

u 0 M-(

%

m c \ 0 c %

(X ItJ 0 01

m 0 0) rH O £ l Q> 04

iH -H 0

iH 0

CO V •H 0 E -d c (0

n n \ Id

a % p. m o (0 M-l O

<u rH 0 E u 0) 0,

rH 0 ^

o o iH 10

m 0 (0 0) rH O s •• TC

0) H

X) <d H

+ 0) c 10 rH (0 ' 1

c + '>< -H PM N — i '

+J

• r-t

e n +

•H FM -'

0)

(0 M (0 0) 4-» Ui

g p

-0 O 0)

• 0> »H

tM

o 73 0) (0 O a E 0 o E 0) -p to >1

n c 0 •H

m r-i :3

E 0) o u u •rj

£

• U 0 o ro -M (0

rH 0 C 10 4J C d)

a <4-l 0

M 0)

E 0 m • r *

0)

(0

«0

CO

E -H •d o to

O B 10 •P

c 0)

04 I o (0

o c 10 +J c <1> 04 I

c

Jo c o z I c

0)

c +J

0) X i c

0)

c (0 X 0)

ac I a

c (0 +> c 0)

04 I

c

c <0 c o I c

0)

c - p

0)

c

n 10 X IV

c 10 • p c 0) 04

to

to

o l (0 c Ic

(0 w

10

roi (0 C (9

10

CO

CO

O l CO C C

(0 CO

0 1 (0

(Ol CO

c Ic

0 1 CO

c Ic

lOl CO

c Ic

0 1 CO

c Ic

lOlf « Cr.lc

CO 00

VO

o

CO

ON ro

in

ro CM

o O

o 00

• VO CM

CM

in

iD

ro ro

in

\o

VO

ro in 00

o

CO

VO fO

• ON

o

CO

Ov

o CO

ro ro

VO ro

VO

ro ro

CM

CM

CM

O CM

in

CM CM in

00 ^ rH 00

CM

CM •

VO

• « * 00 in

00 in

• CM

in

ON

CO 00

* in

CM

o in VO

CM CO

• CM

ON

VO

o in

in 00

« ro CM

in

ro VO

o ro

O

• ON VO

00 00

• VO

00 00

• 00

r-

in m

n

in ri % ro CM

O ro •

in

ro •

VO CM

in ^ • i"

r • •«t ro VO O •

r-

'd' •

<^ ro ro O •

VO

r-CM •

VO •Sj'

o r-• 00

00 in •

CM tn

ri" in •

r*

CO 00 •

r-in o ro •

o T-1

o r-• in VO

O ro •

o\

o •* «

c VO

o o • CM TH

03 00 •

00

r-tn T-i 1 •

tH

CM

in

o ro

• OG CM

rvj

o CM

ro

00

CM in

00 00 •

VO TH

o in •

VO

00 TH •

rH CM

00 in

ro ro •

in CM

VO ro •

00

VO

c>-• rH ro ro ro

O 00 • ro ro O ro «

O rH

ro ro •

rM •*

00 rH

^ CM •

CM ^

^ CM •

CM rH

•^ <^ •

CM in

CM rH

r-VO •

o in

ro ro •

•^ rH

rH in • ro VO

O O

CM rH •

ON in

o • ^

• VO rH

O T-t «

•^

r

CM CO

113

12il

D Q

o

<£>

( S u / ^ U )

doos |0 aiotu j ad loqooio |o saiOlM

— ro

"o E

D (/> i_

>

C

o c

en c o c a o o

° § O H-

E o

CD O)

O CD

>:t (O

CO v j

CM CO

C9

a • — o »•-o Ctf

"o

o E i_

w a

o x: o u

H -

o

"o E

«•-o (A

t/1

•D C9 yj o a E o o

E

>> w c o w

E c* o l_

o

c o c

a c o o § L- C <S I

£ c o .15 0 • D

C o

C

o

o I

C

E

o ^

w 2 F o o

C

a o o

CO

o

(n >•-

o Ci>

• • ^

o E L.

X

L L

c •*J

a u O (9

a V)

c o a r.

I

c

c O K

J: I

c

(9 c o ••->

C

a

u o

«»-l

% 0)

C \

0 c

% P4 (0 0 (0

*u 0

0) r-i

o E

u V (k

t-t •ri 0

M-l

o (0 0)

i H

o e -d c <o % m

c \

to c »

p^ (0 0 (0

U-l 0

0) f-\

0 e u a

H O ;c 0 0

i H

n) «w 0

(0 t>

i H

0

s . ••

tn

0 • H

X) (d H

+ - X

• H PM

> — L4 0) 4J (0 ^ •

r ^

+ 1< • H PM

% • * '

0) 4J

- H

. H (0 a g

• H 73 O 0)

• D»

t H

*U 0

•0 0) (Q 0 Qi

E O o

E 0) 4J (0 > i

«) c o •w to

i H

3 E 0) 0 M U

i H

E 0) Xi -p

• o 0 o n

+» 10

r H O c (0 +J c 0) p.

H-l 0

M 0) E 0 to

• H

+ 0) c (0 >: 1-1

m 1 c

0)

n) •P

O (0

r-l 0 C ID •P

n 0) CL< 1 0 m H

i - t

0 c (d •p c « a, 1 c

0) c m c 0 2 1 C

0) a rO 4J D, (U X 1 C

0) c (0

Q) X 1 c

0) c (0 • p

(U & 1 B

Q> B <0 B 0 2: 1 B

(U B m -p A 0) K 1 B

0) B m X 0) K 1 B

9) B (0 •P

c 0) Oi 1 c

1 0 U) C I B

1 (0 m fl I B

1 0 m B I B

1 03 W

c Ic

1 0 to B I B

1 (01 to B I B

1 ol to B I B

1 (dl u) B I B

1 o n B I B

1 m in B I B

1 0 to B I B

1 m to B I B

1 0 (0 B I B

1 10 to B I B

1 0 to B Ic

1 « to B la

r~ • ^

• i n r^

CD CM

• VD

CM

^ •

a\ r-i

n 00

• i n

CM cvr

• «H CM

CM

r~ «

i n

^ i H

• t C CM

i n CM

t

i n

r> Tj"

• in rH

r (j>

• i n

CM • ^

• o\ T H

f O in •

i n

CM CM

• T H

CM

in i H

• in

r-t • H

• ^ CM

\o CO •

^

CM (Ni

• n CM

\o CO

• t~-

i H r-i

• c CM

o CM

• r o CD

• ^-t tn

O CM

• r-

t - (

T-t

• \o m

00 i n

t

VO

CM CM

• m CM

rl T-i

• r-

r-<

r-i

• a\ CM

r> \D •

VO

o 0 0

• r H f O

r-• < *

• VO

r H r-i

• VO n

">* OV

• in

o o *

r H

n

VO i n

• Ov

O CO

• CO n

00

r •

CO

o • ^

• CM

^

^ VO

• 00

o CM

• 0 0

•^

r H

r H

• 00

o o

• r H

n

c • *

• 00

o 00 •

00 n

in r> •

r~

o "«t

• CM

•*

c VO

• r-

o CM

• 0 0 • « *

VO

o •

r*

CM r H

« 00 m

CO r H

• r-i r H

m i n

• 00

•

VO en •

o r-i

VO O

• n in

00 r H

• o rH CM CM

« O VO

•<* VO

• a\

04

r-•

CO

m

o t~-

• tJV

n in •

00

•

"* CJV

• 00

VO

o • n

i n

CM

r •

00

CM CM

• o VO

VO CM

* 00

• *

•«* •

yo • *

CO

r-•

CM rH

CM CM

• CO i n

ro 00

« r H

r H

VO

o •

VO vO

• VO

• rH rH

o n

t

CM t -

CM CM

• T-H

Tj<

• ^

• VO ••t

r--»H

• r H

•r-i

CM CM

• 00 in

CM CM

• O rH

VO O

• VO VO

O CM

• o rH

O CO

• CM

r-

en o •

OV

121

o CO

to

CO

CO

C9

(A

O CO

GO

CM CO

- CD

H- a

CM

IJ.

(Su^'^u)dDos ^o aiouj j»d loqoDio ^o S3io IN

M 0

iw

% n

G \

0 C

% Q< (0 0 (0

4-1 0

a> i - i 0 e u 0) a

c-H TH

0

»w O

U]

a> rH o E -a c (0

% 01

B \

10 B

« a< s iO

m o 0) H 0 E U 0) A

H 0 4: 0 o •H ro < O

(Q 0) H 0

s ••

VO

4) H 4) 10 H

+ * • — ^

X •H P4

—' M (U +-) ro 3;

rH

E ro

+ 1< •H PM

SM>^

0) •p 0)

(0 •H W4

>, E p

•H -a o 01

• en

t H

m o -a 0) 01 0 Oi E 0 o E (U

01 > 1 01

B O •H in

rH 3 E 0)

o M O •H E 0) x: j j

• o

o o n

• P (0

rH 0 B ro •p B C) a

«W o M 0) E O w •rH

+ 0) B ro X r H <0 1 B

0) -P ro -p 01

•H iH

>

•H -0 o w

<-i

o c ro •p c (D ft 1 0 w H

i H 0 B ro + j B (U cu 1 E

0) B 10

c o z

1

c

E m +j D4 Q) X 1

E

0) E ro X 0) X i

B

•

0) B ro + j B

<u ft i B

E ro B 0

B

0) B ro •P Oi v X 1

B

0) B

(U

1 B

0) C ro •p B ft 1 B

O m c IE

ro 01 E IB

01 (0 E IE

roi (0 B IE

o m E IE

rol 01 B IE

O 01 E IE

rol 01 B IE

00

CO VO

in

o rH

ON

en

i n

in «

T H

CM

O

in

o CN

ro

VO CM

in o

ro VO

ro

in ro

• CO

CO

CO CM

CO VO

VO

o in

CO

ro in

• VO

00 ro

CO

o CO

00 ro

* ro

o

vC)

ir

0^

in

r-^ in VO

o CM

in

00

in

o

in CM

in

in ro

(Tl rH

o in VO

00

1 0 n B I B

1 rol 01 E I B

1 O 0}

B I B

1 rol 01

c IB

1 O 01 B I E

1 roj 01 B I E

1 Ol 01 B I B

1 <0| 0)

a I B

ro a\ • ro

»H

O VO

• in

00 • • t^

»H

O ro • i n

o i H

• o\ »H

00 o •

m

in '^ • i H

CM

00 00 •

• *

o <r> •

o CN

in VO • VO

o CM

• VO CM

ro ro • VO

ro VO

• CO CM

ro TH

• VO

o in • CM

n

in 0^ •

in

CO 00 •

r-CN

o 00 •

r-

ro o\ • •*

ro

i n vO

• t^

00 t H

• CO ro

O ro •

<J\

00 ro • ro

^

00 O •

r-

in 00 • • j"

fO

ro O •

a\

00 vO • n

^

00 t~ •

CO

i n

r-•

r~ Ti"

o in •

00

o CM

• M-in

ro CN

• 00

ro CO *

T-*

•^

ro ro • O

o • ^

• CM in

o T H

« o TH

in CM

• r-i n

ro VO •

ON

r-o • i n

VO

o ^ •

<

LLI

1-< 1-C/) —

cc >

c C9 Q.

o V)

1—1

. 1

D O O

o c a o o w

C9

o E L.

a

o

o

a E

D

O

"o E

u o O CO

124

II)

c

o c a o o

o •o

0) o a E o u

E

o c o

••->

c a c

o o § L. <= C9 I

E c o

— 0

T3 C o

O - ^ o

o

a o x: o u

en

C9 c o

c ^ ,2 o

I D C E . O K »_ —

o u. E ^ k < o •>

c o»

o C

cy O E

o U)

o K.

a. o o w o

c» o E

u. , ^

<s 0

(0 L. >. E

CO

at i l

c o a

j i I

c

C9 c o X

x: I

c

I

X — O c o

•4->

c a I

c

( S U / D U )

d o o s jO a ioo i j a d l o q o o i o ^o s a i o w

rf'-N

i^ " s - ^

4)

e* 0 rH (0

% * - N

0 (0 X

" w '

0) (0 (0 x: ft rH •M O

(Q 0 O 3 c •H

+» c o u c •H

•0 c (0

• ^ - N

• ./o K "^ 0) u (0 •H U <u +> c •M

0) j :

+» +> (0

H 0 ^ 0 0 r-t (d >M 0

c o •H +J O (0 M

IH

Q) i-l O s •

r-« r-t X) 10 H

X •H •4

(U •p ro (0 a> •P m

E -H TJ 0 «

C7<

TH

m o -0 0) 0)

o ft i u E 0) •p n > i 0)

c o 0)

rH 0 i o u o •rJ E 0)

JC •p M O m

0 n O

0 •0 c 0

-» H v.^

•P ft 0)

a Q> 4i C •r4

• o 0 o fO

•P (0

rH 0 c R) *i C

ft «H

o u 0) E 0 m •H

«•• -

(U c (d ^ rH (d 1 c -*.

1 ^ - ^

X •A fu 'o^^

U V p 10 >

D>

ro

o c (0 •p c <u 0* I o (0 H

o c

c 4) PU I E

0) O to rH

O O

a 0]

II

0 ( d c

&

O (0 X

•H (0 X

0) O m rH

O 0

*Ȥ I b

c (Q

H H

o <o X

/d

0) c

rH

c

00

c CO

C>1

in

CM

in

rH

O CD

in

in cvi

o o cv

en in

CO

o

o CM

o

\o

c

•p c 0)

o 00

o in

o

o

01 c (0 X

c

o o CM

in

T-I

o

0) c (0 ft V

c

rH O •

125

o »-»

•

(N - l"

* o r-

•

in o

• CM

ro

O

CM

ro en

O

CM

CO CM

00 00

0) c (d

g c

0)

0)

O (0

0)

+ X •H

<0

10

+»

A

o 0)

•H 0»

o .-< (0

s c

+>

s o

•0 c (0

1 ^ o

0) 0}

o ft

.(0

o Id •H M 0) +> G •ri 0) •p

O x: 0 o

10

t«-l O

C o •H

o u m 4)

o

00

0)

r-t

(0

o E <u •p 01

c o •H (0

i 8 o e

•p

o

O 0)

o <3 •o c (0

+> Pk (0

o

a •A

o o o fo

+> (0

o c (0 +> c 0) (U

o

§ (0

0) c (0 X (0 I c

PM

V4 0) •p (0

D>

CO

O c 10

c Q)

CU I o

H

O C <0 •P C (U

I c

o

O n O <J I

c ic

"Sic" &

0 (0 X

^^«

0) H o

i O 0)

I

|H(0 Vi

II H

|O(0 O

c Ic

^

O (0 X

0

9) c (0 X iH

7

CM

cs

o

00 CM

in

o in

r«4

in

o

CO

o

00

00

CM

O

CM

VO

o in

in

00

CM

O

0\ OS o

CM CO

in

00

CM

in

• o

CM

CO

o

O CM

o

in

VO

ro 123

in o

CM

ro

in

o

m CM

o CO

VO

O

ro

O

VO

0) c (0 •p c 0) a< 1 c

0) c n) X 0) X 1 c

Q> C (0 P ft (U X 1 c

(U c 10 c 0 55 1 a

i4

0)

n

O (0

0) V)

m 0 O c •H +> s o c

c to

<o

9) O (0

•P C

(0

o x: o o (d

in o c o -H •p o (0

u

0)

o

rH JQ (0

X •H

+> (0 •p 0)

M > i E

•H

o 0)

b»

O tH

o -d 0) m o § o

§ •p 01 > i (0

c o • H CO

iH

i 0)

o o

0)

o

O 0) o

•d c ID

U O o m

•P 10

o C <0 4J C 0)

O

to •H

c

(0 I c

•p

0)

0) •p c

u

tn fO

o c (0 •p c a> I o (0 H

o c (0 -p c 0) cu

I c

0)

o

f o n o <

I

pto m c c

0(d c

t!

O (0

.nJ

0)

0

O CQ

o

I

(0 (0

0(0 O

c Ic II

O (0 X

(0

c A:

to I

c

CO VO

in n <N

in

o

o rg

in

o

O

VO

cr« o

en

o

in

CM

in

CM

in

in

CM

in o

in

CM CM

in

CM

VO

o

in

in

n

o CO

in

VO

127

CM CM

CO en

00 VO

^ • ^

r -t^

<u c (0 -p c <u QU 1 c

0) c (0 X 0) X 1 c

0) c (0 -p ft 0) X 1 c

0) c (0 c o z 1 c

O

O

a E O

L

en

o

I

G)

CO

O

- CO

- in

- <r

- O)

- CO

©

u

- to

- LO

CO I I

i n I

c O

I

c

c o n u

c

o c

£ o

c o

o o

128

E 3 C

o c o c a. o tn

^ o

< o

o 2 c

C C9 O Q .

V> I

.5 c L.

> •

.5* Ll.

• • - •

c o

louj/rvi SQOV

^ ' ^ r Sodium myristate

-4-0 o E

(/) o CD <

- 5 - 0 -

- 6 - 0

©

n

123

8

Fig, 4 Variation of Z \ G | with number of carbon atom^ n^, in alkyl chain of n-alkane

• : n-Pentanol , o : Iso Pentanol

en t-l

M-l 0

•0 Q) in 0 a e 0 V

V) c 0 •H (Q iH

S> E 0) 0 M U •W E M-l 0

0) O C (0 •p 10

•a (Q 0) V

0) ^ +J

c 0 0 •H -p (0 M

r-« -H 0 \ u (U -p m ^ tp

o •p

o 0) M-1 M-l U

•• O rH

0) iH

Xi (0 H

c p c 0) a 4-1 0

M 0) e 0 c: •<-(

fH

E CO

+ 'x •H PM ^^

Q)

>; .H (0 1 c rH

E o

+ ^ (U •p

3

+

'K •H PH V—'

<u -p (0 u m (D V Ui

E p •H TJ O V)

• U O o CO •P (0

*- X iH ^ ^w*

<1>

M rO 0)

+J CO

o to

o in I

0) o c (0 -p m •w (0 0)

o c (0 -p c 0)

o

o c (0 •p c 0) I

c

s o o;^

0) c (0 -p c (U

I c

0)

c (0 X 0) I

c

0) c (0 -p p< 0) K

in vo •

rH

in VD •

rH

O VO • -1

Q) C (0 •P

c 0) I

c

0) c to X 0) sc I c

0)

c •p

I c

o O 00

o o CM

O

{VJ

O

CN

in in vo r^

« I »

o vo

o 00

o o

t CM

o t o in vD

t •

o o

in

CM

o

o 00

o 00

in 00

o

o VD

CM

CO

o in

in "51*

•^ « *

in CM

130

CM

o •*

• a\

00 in

in n

00 CM

• < *

CM CM O CM

in

o

CM CO

I * I o

o •<*

o CM

in (T\

00 VD

a\ in

CM in

CO xj«

r-i

o o T-(

• o

o in r-t • o

o o CM • o

in CM CM • o

o in CM • o

o o CO • o

«n CN rn • o

o in n • o

o o •* • o

in CM • *

• o

o in • > *

* o

in t M< •

O

131

D Q O I/)

o c o

• • - '

c CL

I

c

CM

CO

- I - J_ 0 0

CM CM

O

CM iO CM 00

t

o o

6

If)

6

6

CO

b

CM

6

ID

O

in

6 <r 6

CO

6

CM

6

._l o o CD

>

>

o

o

••-»

o

>

>

o c 3

•M O

o

O c o

-

O O

C9

c o

l_

O I

••->

••^ o 0 >-

- ^ o 1 «^ CJ tf,

E o D O ^ ' ^ O -M

CO O _ C

o I-; — ° O

' - c o -

C "D C9 C» Q. U) O H-Q. O E ._ o u E

••-' w >.

c o

E

o L.

o

C9 JZ

>

IT)

Q)

a I

I

c

E o (A

E 00

•D c

C9 c O K

X I

c

i5 o

c o

"o I c

C9 c o c

a. I

c

c o

9

• D>

i-t

M-l 0

Ti 0) (0 0 P< E O U

(0 B O •H (Q iH 3 E 0) 0 M o •H E «M 0

0) o B nj 4J m

•H n Q) M

<u X +) c 0

0 •H P <0 i^

rS •H 0

\ t-l (U -p rt> ^

m o +J o Q) i « M-l

u

X •H PM

- t-i 0 c (0 p c fl)

a H^ 0

u a> E O in •H 1

r^ E 00

+ - X

•H

w

0) c ro

>J rH « 1 B

rH E

o 1 - )

+ M 0) P (0 ? + - X •H P4 - 0) +J rO 4-> •iH

e iH n a

u e 0 3 o •H fO

n 0 V (0 (0

I-t

(0 EH

I

0) +> ro +J •rl

E iH 10 04

E 3 •H -d o tn

in 1 o rt

X Q)

o B Id

+> 0) •H (0 0) Q:

rH 0 B (d +J C 0) 04 1 0 m H

0) B (d +> P< « 04 1 B

(U B «i X 0) K 1 B

o B ro +J B 0)

04

I B

0) B (d •P 04 0)

I B

0) B Id

P4 0)

04 I

B

0) E Id X <u X I B

(U B Id + j Qi <u I I B

O U) CO • *

• •

CO in

o in fo in CM 00

• * • »-» t-( O

CM CO

o

in CM

I •

o 00 CM

vO 00 CO

CM in

i n

tH rH O

00 CO I •

o o VO

CM o CM o

cr> o

o o CM

o CN

o CN

in CM

i n o CO VD

1

i n CM

•

o m •

o • *

•

i n • ^

•

i n m

•

00 VD CO

P-00

< r-

00 VD

i n m

c ro

n CM

132

o o

CM O •

o 1

n o •

o

VO ro

CM

00 t>-•

o

ro VO •

o

o i n

• o

00 CM

• o

CM CM

• o

U O c -<J) -H > •P >H + J \ Id -H rd > IS o oj —

o o tH

o

o in rH

o

o o CM

o

o in CM

O

o o ro

O

O in ro

o

o o • < *

o

in (N • *

o

o in ^

o

in r-T*-

o

o o in

o

in CM in

o

o in in

o

o o VD

O

133

UJ I-<

< Q.

D Q O if)

q o

o

o

o

£ o

I

"o ^

C9

O

c ^ o > — > c

o ^ u E o

"T3 ^ O O

(/) ^ • "o

cn c

«•- O

o

o c o (/)

o

•D

o a 6 o u

E • c •*^ c y) >^ CD

c ? .9 o

C9

E o

•«-> en

c o

O >

CD

Li.

3 E o u

C9 £1

C9 •»->

O

c D

a I c

^ C

C9 C

o X X

C9 C O

£5 I

c o

••J

c CL

liJMO OL /aouD^sisay 9

• Di

»H

m o T) 0) U) 0 0< E 0 o m C 0 -H 0}

•H 3

e 0) 0 M O

•H E

«H 0

u o c « +J m

•H CO 0) >-i

(U £ +> fi 0

o •H •p (0 t

i H •H 0

\ ^ 0) •p ID ^

>« o +i o 0) m <w u

X •H PM —'

r-i

o c (0 +J c • a. tp 0

u 0) B o v> -H

H E 00

+ < (U •p

m ?

+ *•-% X

•H P •—'

0) c <0

X ^^ <0 1 c

f - l E

o rH

+ l ^ " ^

X •H PM

N * ^

0) -p (0 +> (0 •H i-l N s

u E 0 3 o •rl m n O +J 0) (0

fVJ

0)

EH

•P (0 +> to

c w

I E o

in I

0) u c n) •P (0

•H (0 «

o c (0 •p c 0)

I o w

o c (0 • p c 0)

I

a

c -p c 0)

I

c

0)

(U X

I

c

0) c (0 • p

0)

I

c

0) c a -p c 0)

I G

0)

c X

a: I

0)

P. 0)

I

U 0>-; <U -H > -PrH + > \

s o os^

a

00

CM t H ^ <T> OS 00

• • • o o o

• • o o

CM CD

iH n vo r r» r-• • •

o o o

VO

r r

CO

CM

CTi in

cr>

lO iH

• • o o

in

CM

CM

o

VO

o

CM

vn

r in •

o

n in

• o

VO • * •

o

c» n

• o

.H

n •

o

CM CM

• o

ro

CO CO

CO

n

o o

CM

m o o

o CM o

o

134 ro o o

ro o o

rH O O

i n

o o

n o o

CM

o o

0<«

o o

CM O O

o o

o o

• o

in rH

• o

o CM

• o

in CM

• o

o n

• o

in CO

• o

o •^

« o

in • *

• o

o in

* o

in in

• o

o VO

• o

in VO

• o

o r-

• o

UJ

cr >

D Q O

c 0

• •J c ( a. 1

• c

1 •

,

^ ^ .

1 1 1 1

O

6

in 6

<r 6

CO

6

CM

6

> >

o

o

o

> ?

. 9 o

o o

I - .y?

- i O .5

135

c o

••-» (J c 3

H-

o in o c o r

in

L.

TJ O (J)

o •a in o a E o u E c» in >

o o O en

O

o c O • 4 - '

c c a <*-o t_

E

vy 1_ O

a I

1

c • *

( c O X c» I

1 _, in O o

c o

c o

3 E G) O I . O

E 00

•o c o

C

o

5 . £ <

o in ~

•^ o

C9 C O c

CL I

c

CM 00

6 6 •4-6

CN o

6 ^MO 01 /30UD;s i say

5

CP

*u 0

TJ Q) (Q

0 D. E 0 o c 0

• H (0

r ^

3 E 0) 0 u 0

• H

E M-l 0

0) o c (0

•p (0

• H

u 0) u c 0

c 0

• H •p (0 w 4J

c 0) 0 c 0 o r-l 0 £ 0 o

i H nj

m o +J u 0)

IM

«u u

M-t 0

M (1> E 0 V)

• H

+ „^ X

• H PK v»^

9) c (d >; rH fO 1

c

E

o f H

+ *^ -N

X • H

fa - u Q) - p m >

r H

E

n

+ ,*—>, X

•H fa **-•'

0) •p (0 u (0 9) +> (0

E 3

• H 13 C (0

U O o fO

•p fO

r-i O c (0 •p

c (U ft

n

0)

(0

+J

to +> CO

•w

o in I

0) o c +J m

•H (0 <u OS

o B m +> c <0 a I o m

o c (0 4J C 0)

I

c

0) c (0 •p G <0 cu I c

c (0 X 0) X I

B

01 B CO

- P P< 0)

I c

(V c (0 -p B (U (X I B

B (0 X (0 X I

B

(U B to •P ft 0) X

B •H E

M-l M-t 0) O O rH +J

O (0 (U >-i B >i'-« E <U (0 V) iH 3 E -p e i-t O E a)^--O W 0) JS > H fa +J

o CM

• o »-l

1

o in

• r- 1

in CN

• in

1-o o\ 1* n

133 in o o CO n 00 vo vD a> in TH CTi r^ vo

(N o o o

o 00

I • ON

I I i in

in I I

in T-i

* m

1

o CO

• ri

o m •

T-i 1

•'t CO •

o

n r-•

o

I I

CO

o I I I m

•^ i *

o CO

CM

in in

O 00 ^ O t ^ Tj. ^ Tj< • • • • o o o o

o in

I I CM

o O o

en

o o in vo in ro CO CM i n »-t 00 vo i n ^

• • • • • • * (N <-t t-H O O O O

00

• ^

o in •

CM 1

o a\

fl

r 1

o o •

in 1

o ' i t

• ro

1

in c •

t-4

in CN

• r-«

m r-•

o

in in •

o

o •^ •

o

CM f O

• o

o m •

o

o o o o o o r vo <}< o in

a\ in in

r-r-

in r-in

CM •sj*

CM

n CM CM

vo rt

CM

i n i n VO vo 00 cy>

137

UJ

< DC < UJ \-

D Q O (/)

o o o

C9

E

o >

^ E .E o

o i : o o

E

• • J

o

CO

I

— o o > o O (fl

c o

o c

O

O c o

w W (A

O o

u

£ o

"D O O o

CO O . CO

(9 c o a X

I c

in o a E o u

° g 2 g Q- I

c E fe (/) O in —

« .b

£

"o >

C

o

E C9 o o

T3 C

o c O

"o I

c

CD

L L

c o c a

I

c

138

DISCUSSION

The fact that the partitioning of alcohol and surfac­

tant at the interface is responsible for the stability of

the interface and hence the microemulsion droplets. The

stability of the interface is also responsible for the

water solubilizing capacity of a water-in-oil microemulsion.

The larger the stable surface area of a microemulsion droplet

the higher will be its water solubilizing capacity , If micro-

emulsions are considered to be stablized by a mixed film of

surfactant and alcohol, the nxomber of alcohol molecules per

soap molecule would depend upon the partitioning of alcohol

between oil, interfacial region and aqueous phase. The

partitioning of alcohol between different phases would also

depend upon the nature of additive and the chain length of

oil, alcohol and surfactant. The number of alcohol molecules

per soap molecule are also responsible for disorder. of

the interface. This together with the magnitude of interface

would dictate the water solubilizing capacity of a micro­

emulsion. Thus higher the disorder. created at the

interface of a microemulsion droplet more will be its

water solubilizing capacity. The alcohol chain length has

been found to affect the ionization, inferfacial polarization,

and disorder at the oil/water interface which in turn influ­

ences the solubilization capacity of a microemulsion system

139

among its other properties.

The water solubilization capacities of sodium stearate,

sodixim palmitate and sodium myristate microemulsions as a

function of alkyl chain lengths of oils and alcohols are

shown in table 1. In all the systems 8 ml of alcohol, 1 g

of soap and 10 ml of oil have been used in preparing the

microemulsions. It may be seen from table 1 that for n-

butanol and isobutanol microemulsions the roaximvun amoxint of

water solubilized decreases continuously with increasing

chain length of oil, whereas for n-pentanol and isopenta-

nol it increased continuously. It may also be seen that

water solubilization capacity of normal alcohol microemuls­

ions is higher than that of their branched chain isomers.

The increased water solubilization capacity ofpen-

tanol microemulsion with increased chain length of oil is

due to its preferential partitioning at the interface. When

water is added to the system the size of the droplet also

increases resulting in a concomitant increase in the inter-

facial area. Upto a certain extent the alcohol from the

continuous phase can transfer to the interface and stablize

it. The transfer of alcohol from the continuous oil phase to

the interface would also depend upon the solubility of alcohol

140

in the continuous phase. In case of pentanol and isopentanol

microemulsions, the alcohol partitioning increases with the

chain length of oil, hence its water solubilization capacity

also increases. An opposite behaviour is observed for n-butanol

and iso-butanol microemulsion systems. This is because these

202 alcohols are highly soluble in water than pentanol , hence

their solubilities in the oil phase would decrease with the

chain length of oil. Therefore for a particular oil more

alcohol molecules are expected to be present at the inferface,

in combination with soap molecules. This, in fact, also

produces greater degree of disorder at the oil/water interface

leading to higher water solubilization capacity of a micro-

emulsion as compared to pentanol.

Frcxn the results in table 1 it may be noted that the

branching in the cosurfactant chain e.g., isopentanol and

isobutanol decreases the water solubilization capacity of

microemulsion system as compared to their normal counterparts.

This effect of branching in the alcohol chain could not be

explained only on the basis of their mutual solubilities in

the various phases and their transfer from the oil phase to

interfacial region during water solubilization. However, these

isomers when partitioned at the interface form mixed alcohol

plus soap films of lesser disorder between oil/water interface.

141

This infact decreases the water solxibilization capacity of

a microemulsion system in presence of these isomers of

alcohols.

The water solubilizing capacities of sodivun stearate

microemulsions with 2 g of emulsifier are given in table 2.

These results indicate that not only the partitioning of

alcohol but also the amo\ant of emulsifier is responsible for

the water solubilization in the microemulsion system. This

120 behaviour is consistent with the previous findings

Table 3 shows the solubilization capacities of con­

ventional surfactant (SDS and CTAB) microemulsions. It could

not be possible to produce a microemulsions by using 8 ml of

cosurfactant as in case of soaps, therefore 5 ml of cosur-

factant was used. The results in table 3 show that the water

solubilizing capacity of CTAB microemulsion is higher than

that of SDS microemulsion. It may also be noted that SDS

microemulsions with all cosurfactant combinations ishow a

decreasing water solubilization trend with increased chain

length of oil, whereas CTAB microemulsions how an increas­

ing trend with n-pentanol and isopentanol and a decreasing

trend with n-butanol and isobutanol. This difference is

possibly due to the micellar structural differences existing

as a consequence of head group size and stearic requirements. charge

Since the positive/residing on the quartemaiy nitrogen

142

of cationic micelles is less exposed than the negative charge

of SDS micelles, the proximity of the counterions to the

head group is less in cationic micelles and as a result it

affects interaction with water and therefore water solubi-

lizing capacity . In this concentration range no micro-

emulsion formation was observed when n-octanol was used as

a cosurfactant. However, microemulsion could be formed by

using iso-octanol (2-ethy-l-hexanol)- CTAB combination

(table 3). This may be probably because with n-octanol

cosurfactant the oil chain length plus alcohol chain length

exceeds the effective chain length of emulsifier, producing

a region of disordered hydrocarbon chains near the terminal

methyl groups around the droplet which is responsible for

destabilization of microemulsion droplet. It was reported

that the maximum solubilization of water in the system was

observed when oil chain length, L , plus alcohol chain

length, L , equals the surfactant chain length, L„, for a s

anionic surfactants and L -4 for cationic surfactant s

(CTAB) ' . In case of isooctanol the region of dis­

ordered hydrocarbon chains near the terminal methyl groups

around the droplet becomes less probable due to the presence

of an ethyl group at position 2- in the alkyl chain. These

effects favour the stability of the interface and hence the

water solubilization in the microemulsion system.

143

Figures 1-3 show the plots of n /n^ versus n /n for ct S O S

different oils and isomers of pentanol combinations (Tables

4 to 6). From the intercept (I) and slope (K) of these plots

the values of number of moles of alcohol per mole of surfac­

tant at the interface and the number of moles of alcohol per

mole of oil in the continuous phase respectively were calcu­

lated. The interfacial data for sodium stearate, sodium

palmilate and soixim myristate microemulsions are sximmarized

in tables 7 to 9. It is clear from the results shown in

tables 7 to 9 that the mole fraction of alconol at the

interface (X_), calculated from the number of moles of alcohol

per moJe of soap, increases with the chain length of oil and

decreases with the chain length of soap in the system. The

increasing value of X^ with the chain length of oil clearly

indicates that the water solubilizing capacity should be more

for higher chain length of oils. These observations are also

consistent with the results reported in table 1. From the

values of I in tables 7 to 9/ it may be seen that branching

in alcohol chain produces less partitioning of alcohol at

the interface than its normal chain counterpart.

The values of free energy change,A G°, for the tran-

sference of one mole of alcohol from the continuous oil phase

to the interfacial phase are also tabulated in tables 7 to 9,

A perusal of these ZAG° values indicates that the branching

in cosurfactant chain partially controls the transference of

144

alcohol from oil phase to the Interfaclal region. A plot of

A G ° versus alkane carbon number, n , results in straight lines

(Fig.4). From the slopes of these plots the free energy contri­

bution per methylene (CHj) group of oil chain for the trans­

ference of one mole of cosurfactant was calculated./^G /CH^

was obtained 250 J/roole which is in close proximity with the

205 reported value of 230 j/mole . The free energy contribution

per methylene group of oil was foxind to be independent of the

alkyl chain branching of cosurfactant and the chain length

of emulsififer.

The electrical resistance variation with water/oil

ratio (V/V) for different soap systems is shown in figures 5

to 7. These figures show that the electrical resistance

first increases slightly upto a certain water/oil ratio in

the system and later on it falls off rapidly. This is

possibily because below a critical volume fraction of water

in the system, called percolation threshold, the droplets

are isolated from each other and contribute little to the

conductance of the system so the resistance increases slowly

in the begining. However, when the volume fraction of the

dispersed water phase exceeds the percolation threshold,

seme of these droplets begin to contact each other and form

clusters with many conductive paths. Conductivity therefore

begins to increase rapidly resulting in a rapid fall in

electrical resistance of the system. In almost every system

the resistance of the microemulsions was found to decrease

14,

with the chain length of oil for the same water/oil ratio

in the system. This behaviour is possibly due to the higher

values of n /n^ (I) at the interface with increasing oil a s

chain length. The increase in n /n value causes the inter-a s

molecular distance between soap molecules to increase resul­

ting in greater degree of ionization of soap molecules leading

to a decrease^in resistance of the system. This electrical

resistance behaviour of microemulsion systems indicate^that

the thickness of ionic atmosphere within the microemulsion

droplets increases with the increase of oil chain length.

It may be seen from figures 5-7 that at the same water/

oil ratio the electrical resistance of branched chain cosur-

factant isomer is higher than its normal chain counterpart.

From this it may be inferred that the branching in alkyl chain

of cosurfactant hinders its partitioning at the interface as

well as affects the disorderedness at the oil/water interface.

The decrease of n /n (I) by branching at the interface a s

decreases the intermolecular distance of the soap molecules

and reduces the ionization of soap molecules at the interface

in comparison of normal chain isomer and thus the surface

contribution to the total conductance will decreases leading

to an increase in the electrical resistance.

Figure 8 shows the variation of electrical resistance

as a function of amount of added alcohol in the microemulsion

systems. The electrical resistance decreases sharply with

14o

increased amount of alcohol and later on becomes constant

at some critical amount of alcohol. The initial fall of

electrical resistance with the addition of alcohol may be

due to the fact that addition of alcohol enhances the

degree of ionization of the soap molecules at the interface

resulting in a sharp fall of electrical resistance. The

increase in the degree of ionization of a cationic surfac­

tant upon addition of an alcohol has been reported in the

literature , The critical concentration of alcohol is found

to increase with the chain length of oil (figure 8). This

indicates that the partitioning of alcohol at the interface

is favoured by the chain length of the oil as described

earlier (Tables 7-9). It may be seen from figure 8 that the

critical alcohol volume for isopentanol is higher than pen-

tanol. This indicates that higher volvune of branched chain

alcohol is required to saturate the interface and produce

the same degree of ionization as produced by its normal

chain counterpart.

147

CHAPTER « V

MICELIAR BEHAVIQUR OF IONIC SURFACTANTS IN WATER>

ALKYLAMINE MIXTURE

148

In the preparation of microemulsion system cosurfactant

is generally to be used in combination with the surfactant.

Systems forming microemulsions present complex phase behaviour

and the chemical structure of the cosurfactant plays an

important role in such phase behaviour. The main role of

cosurfactant is probably its ability to destory liquid crys­

talline and/or gel structures which oviate the formation of

microemulsions. The most common cosurfactants used in the

preparation of microemulsions have been the medivim chain length

alcohols. From a practical point of view alcohols have been

used in tertiary oil recovery because they bring about a large

decrease of viscosity of the micellar systems used in the process.

From a fundamental point of view, the approach of microemulsions

207 in terms of polycritical phenomena has led some authors to

suggest that the formation and stability of microemulsions

might in part result from their dynamic character enhanced by

the presence of alcohol. In fact, it has been long believed

that microemulsions could not be obtained in the absence of

cosurfactants

Now a days some amines are also getting good recognition 1^1 1R9 ?0R 90Q

in the microemulsions ' ' ' .A comparison of some of

the major properties of alcohols and amines show that amines .4

are weak bases, K. is approximately 10 for most short-

chained amines. On the other hand alcbhols are weak acids and

slightly deprotonate. At the air/water interface, amines are

143

210 more surface active than alcohols . Longer chain amines

211 (CQNH-, C,-.NH^) form micelles and some form liquid

b Z lU i.

crystals (C.-NH-), whereas long-chain alcohols are surface

212 active but do not form micelles or mesophases . These

properties should memifest themselves in the role of amines

in organized assemblies such as micelles, microemulsions etc.

The first reference to the use of amines as cosurfactants

69 is referred in Winsort work . Ahmed et al, mapped the phase

213 behaviour of CgNH-Cl and CgNHj in xylene and water . Pseu-

dotemary-phase diagrams of various amines combined with

anionic and cationic surfactants show large one phase regions

and high solubility of water in oil-rrich regions * .

Loughlin found that the amines exhibited higher amphiphilicity

than all other similar amphiphiles with similar polar head

212 groups , Recently, the hydrophilicity of the primary amine

head group has been found to be much greater than the other

simple polar head groups tested. It was found that acid stron­

gly increased the hydrophilicity of amines and base reduced

209

amine hydrophilicity . In microemulsions, the effective

hydrophilicity of amine/anionic surfactant combination was

found lower than expected, indicating that a specific ionic

interaction between amine and ionic surfactant is occurring

in the surfactant-rich film separating oil and water domains.

150

The aggregation pattern of ionic surfactants span a

wide variety of morphologies in water and in water plus

additives, making them ideal model compounds for ccxnparison

between numerous, disparate states of aggregation ' .Of

this class of amphiphiles, those with bromide, chloride and

sulfate counterions are the most thoroughly characterized.

The aqueous chemistry of these surfactants and their aggregates

is highly dependent upon their alkyl chain structure, although

217 several general trends are discernible . Formation of micelles

is not restricted to aqueous solutions. Indeed, micellization

has been observed in a variety of solvents whose polarity

ranges fran completely polar through dipolar aprotic to

apolar. Several investigations have been conducted on the

218~228 micelle formation of ionic surfactants in binary solvents

It is known that addition of an alcohol (in a very small amount)

to an ionic surfactant solution depresses the CMC of the

surfactants^^®'^^°.

An extensive review of the solvent effect on amphiphilic

229

aggregation by Magid has indicated that the continuous

addition of cosolvents into aqueous micellar solutions usually

leads to higher CMC values (but may be preceded by an initial

CMC-depression for many •'penetrating*' cosolvents at low

concentrations), smaller aggregation n\imber and eventually

a break-down of micelles. Three factors are generally consi­

dered to account for the influence of cosolvents on the

151

equilibrium properties of aqueous micellar solutions. The

first one deals with the change of bulk dielectric constant

of a solvent. Cosolvents which lower the dielectric constant

of water should increase the counterion binding, and hence

222 decrease the conductance of the solution. But Zana et al

have found a direct increase in the degree of ionization.

This contradiction between the expected and observed results

thus requires a consideration of second factor. The second

factor concerns the "comicellization" of cosolvents with

surfactants. Despite high raiscibility of cosolvents with

229 water many cosolvents are known to penetrate into micelles

The effect of such "penetrating" cosolvents has been analyzed

222 by Zana et al mainly in two aspects,an increase in the

distance between surfactant head groups (stearic effect) and

a decrease in the dielectric constant of micellar palisade

layer. Both effects can explain the increase of conductance

and the decrease of CMC as a result of dilution of micellar

230 surface charges. A quantitative analysis has shown that

the factor governing the CMC-depression is the mole fraction

of cosolvent in the micellar phase, independent of the kind

220 of alcohols. However, a paper by Manabe et al argued that

the solubilized alkanols in micelles cause an increase in

degree of ionization of surfactants but have little influence

on electrical potential at micellar surface due to a compen­

sation from the dissociated counterions. The third factor to

152

account the influence of cosolvents on micellar solutions

involves the structural changes in water upon the addition

of cosolvents. The hydrophobic association and the micelle

formation have been described in terms of the structure of

water. When cosolvent is a structure-breaker, the CMC usually

increases (hydrophobic interaction decreases), while the CMC

229 decreases when the cosolvent is a structure maker

These interesting features of the effect of cosolvent

on the micellization process prompted us to study micelli-

zation phenomena in a novel type of binary mixtures of amines

and water with the goal of elucidating the aggregation beha­

viour of ionic surfactants in these mixed solvents and to

evolve the possibility of their use in microemulsions in

future. Without investigating their effect on the surface

properties of micellar systems it may not be possible to

directly use them in microemulsion formulations. In the

present chapter very preliminary attempt on the effect of

ethyl and propyl amines on the micellar properties (CMC) of

ionic surfactants has been reported. The results will be

utilized to extend our fucture work on microemulsion system

prepared by using various medium and long chain amines.

153

EXPERIMENTAL

Purification of Surfactants and Solvents:

Cetyltrimethylannnonium bromide (CTAB) and sodium-

dodecylsulfate (SDS) were the same as used in the earlier

chapters, Cetylpyridiniumchloride (CPC) was obtained from

Sigma Chemical Company, It was purified by repeated crys­

tallization from acetone and dried in an electric oven at

50°C to a constant weight, Ethylamine was purchased from

Flufca Chemical Co., packed in Switzerland, n-Propylamine was

obtained from Merck-Schuchardt, West Germany, Both the sol­

vents were used as supplied. Double distilled water having

conductivity 1-2 x 10~ Ohm" was used throughout this study.

Solvent mixtures of amine and water of varying conduc­

tivity were prepared by mixing requisite volumes of an amine

and water in pyrex measuring flasks. These solvent mixtures

were used as bulk solvent throughout the work.

Measurement of Electrical Conductance:

The electrical conductance of solutions was measured

by the same Phillips conductivitymeter as described earlier.

In order to study the effect of amine concentration and its

chain length effect on the CMC of surfactants. Initially a

20 ml of aqueous amine solution was taken in a glass container

immersed in a constant temperature bath maintained at 30 C,

154

The conductivity of the solvent was measured when it attained

thermal equilibrium. To this solvent a very concentrated

solution of surfactant, whose CMC is to be measured, was added

with the help of a micropipette. After mixing the solution

thoroughly after each addition of surfactant the conductivity

of the mixture was noted. The same procedure was adopted for

different surfactants, and amines of different concentrations.

The CMC values of surfactants in pure water and amine solvents

'Were determined at the break points of conductivity versus

surfactant concentration plots. The CMC values of CTAB, CPC

and SDS in water at 30°C determined by conductivity method

199 were in good agreement with the literature values

155 RESULTS

The conductivity data for different surfactants in

presence of different concentrations of amines, are tabula­

ted in tables 1-4, All the conductance values reported in

tables 1-4 have been calculated by applying the solvent

correction to the observed values. The CMC values of

different surfactants in presence of amines were determined

by plotting conductivity versus concentration data (tables 1-4)•

These plots are shown in figures 1-4, The CMC values of CTAB,

CPC and SDS in pure water and in presence of amines are given

in table 5, Tables 6 and 7 show the slopes of straight lines

below and above the CMC. The dependence of CMC of CTAB on

the concentration of amines is shown in figure 5,

156

Table 1: Variation of Conductivity, K, with concentration,

C, of CTAB in different concentrations of ethylamine

in water at 30°C.

C (mMl"-"-)

0 . 2 3 8

0 .455

0 .652

0 .745

0 .833

0 .918

1 .00

1.154

1 .296

1 .429

1 .667

1 .875

2 .059

0 . 0 0 mM

4 . 2 5

8 . 4 3

1 2 . 4 5

1 4 . 3 0

1 5 . 9 1

1 6 . 9 0

1 7 . 8 7

1 8 , 6 6

1 9 . 4 4

2 0 . 0 0

2 1 . 3 9

2 2 . 5 7

2 3 . 5 1

0 . 5 mM

4 . 1 8

8 . 2 3

1 1 . 4 4

1 3 . 2 6

1 4 . 4 4

1 5 . 4 0

1 5 . 9 6

1 7 . 0 6

1 7 . 9 3

1 8 . 7 8

1 9 . 7 9

2 0 . 8 8

2 1 . 5 8

K X 10^

1 .00 mM

4 . 1 3

7 . 6 6

1 1 . 2 4

1 2 . 9 0

1 4 . 8 6

1 5 . 3 5

1 5 . 8 6

1 6 . 3 0

1 6 . 8 1

1 7 . 5 3

1 8 . 6 0

1 9 . 8 4

2 0 . 5 6

Ohm

2 . 0 mM

3 . 6 4

7 . 9 3

1 0 . 4 7

1 1 . 4 3

1 2 . 0 6

1 2 . 5 1

1 3 . 1 8

1 4 . 0 8

1 4 . 8 5

15 .64

1 6 . 9 9

1 7 . 9 0

1 8 . 9 8

2 . 5 mM

3 . 2 3

5 . 9 0

8 . 7 9

9 . 5 3

9 . 7 6

9 . 9 9

1 0 . 2 2

1 1 . 0 9

1 1 . 7 4

1 2 . 5 4

1 4 . 0 7

1 5 . 0 5

1 6 . 1 5

157

I E JZ o

in l O

24 -

20 -

16 -

12 -

8 -

4 -

0

. .

-

-

-

ETHYLAMINE

/ • j*^^^^

1/7 ^^^

//// •y'^^

1 1 1

*,y^ ^.M'''^^

CTAB

1

/ ^ * .^^ ^

^ ^

1

0-A 0-8 1-2 -1

C (mMl )

1-6 2-0 2-4

Fig. 1 P lo ts of K vs . C of CTAB in c thy lam ine

wa te r m ix tu res at d i f fe ren t e thy lamtne

concen t ra t i ons a t 30 °C

158

Table 2; Variation of conductivity, K, with concentration,

C, of CPC in different concentrations of ethylamine

in water at 30°C.

C CmMl'-^)

0 . 2 3 8

0 .455

0 .652

0 .833

1.000

1.154

1.296

1.429

1.552

1.667

1.875

2 .059

2 .222

2 . 3 6 8

o;oo

5 . 2 5

9 . 7 5

1 4 , 1 5

1 7 . 8 7

2 0 . 1 6

2 1 . 9 9

2 3 . 2 7

2 4 . 4 7

2 5 . 8 4

2 6 . 9 3

2 8 . 7 6

3 0 . 5 0

3 2 . 1 7

3 3 . 6 6

K X

0 . 5 0 mM

4 . 8 0

9 .62

1 2 . 9 5

1 4 . 8 6

16 .62

1 8 . 3 2

19 .72

2 1 . 1 1

2 2 . 2 0

2 3 . 4 3

2 5 . 3 9

2 7 . 5 1

2 9 . 0 2

3 0 . 4 9

10^ Ohm

1.00 mM

5 . 0 3

9 . 5 0

1 1 . 8 8

1 4 . 2 1

15 .54

1 6 . 8 3

1 8 . 0 5

1 8 . 9 1

-

2 1 . 2 0

2 3 . 4 7

2 5 . 2 3

2 6 . 4 9

2 8 . 1 3

2 . 0 mM

4 . 4 8

7 . 7 7

8 . 2 5

1 1 . 6 1

1 3 . 8 4

1 4 . 9 8

1 5 . 2 9

1 7 . 0 4

-

1 9 . 3 0

2 1 . 6 2

2 3 . 8 1

-

2 6 . 3 7

153

•E o

in lO

35

30 -

25

IV ETHYLAMINE

0 0-4 0-8 1-2

C ( mMl"^)

1-6 2-0 2-4

Fig. 2 P lo ts of K vs C of CPC in e t h y l a m i n e - w a t e r mix tures at d i f fe ren t e thy l am ine concen t ra t ions

at 30**C

160 Table 3: Variation conductivity, K, with concentration, C,

of SDS in different concentrations of ethylamine in

water at 30°C.

C (mMl"-^)

2 . 3 8 1

4 . 5 4 5

5 .556

6 .522

7 .447

8 .330

9 .184

1 0 . 0 0 0

11 .538

12 .963

13 .636

14 .912

15 .520

16 .667

17 .740

1 8 . 7 5 0

0 . 0 0 mM

3 .247

6 .010

-

8 .495

9 . 5 3 6

1 0 . 3 4 6

10x986

1 1 . 5 0 3

1 2 . 2 6 6

12 .946

-

1 3 . 7 6 3

-

14 .474

-

15 .500

K X

0 . 5 mM

3 .195

5 .926

-

8 .342

9 . 2 6 2

10 .044

10 .514

1 1 . 0 2 6

1 1 . 8 3 8

1 2 . 3 7 9

-

13 .279

-

1 3 . 9 4 7

-

1 4 . 8 0 9

10^ Ohm

2 . 0 mM

2 . 9 8 2

5 . 3 9 8

6 .662

7 .809

8 .700

9 . 4 1 3

1 0 . 0 2 3

1 0 . 4 9

1 1 . 1 0 8

1 1 . 6 6 1

-

1 2 . 5 0 9

-

1 3 . 4 5 9

-

1 4 . 5 2 8

5 . 0 mM

2 . 3 9 0

4 . 6 9 9

5 . 8 1 8

7 . 1 0 3

8 . 0 5 5

8 . 4 7 5

-

9 . 2 7 3

9 . 8 9 8

-

1 0 . 7 1 9

-

1 1 . 6 2 7

-

1 3 . 0 0 0

-

161

2 E o

W

o CNJ

CO

(£> %—

>••

^ o o .;: ^ o i_

r • « - '

1 o O o ">» ,v.

C9

C

(/) O

o u

>

o

o a CO

ii.

E

c

D O .•-» CO K

— • • J

E o

^^0 01/Vl

162

Table 4: Variation of conductivity, K, with concentration,

C, of CTAB in different concentrations of propyla­

mine in water at 30°C.

C (mMl"-'-)

0 . 2 3 8

0 .455

0 .652

0 .745

0 .833

0 . 9 1 8

1.000 •

1.154

1.296

1.429

1.667

1.875

2 .059

0 . 0 0 mM

4 . 2 5

8 . 4 3

1 2 . 4 5

1 4 . 3 0

1 5 . 9 1

1 6 . 9 0

1 7 . 8 7

1 8 . 6 6

19 .44

2 0 . 0 0

2 1 . 3 9

2 2 . 5 7

2 3 . 5 1

K X

0 . 5 mM

3 . 7 8

7 . 7 6

1 0 . 5 0

1 1 . 8 3

1 3 . 0 9

1 3 . 8 5

1 4 . 1 8

1 5 . 1 6

1 5 . 9 9

1 7 . 0 5

1 7 . 9 8

1 9 . 0 7

1 9 . 8 8

10^ Ohm

1.0 mM

2 . 8 5

6 . 0 7

9 .124

1 0 . 0 6

1 0 . 7 7

1 1 . 0 6

1 1 . 3 0

1 1 . 8 1

1 2 . 5 2

13 .12

1 4 . 4 0

1 5 . 5 3

1 6 . 3 7

2 . 0 mM

3 . 3 0

6 . 7 3

8 . 8 5

9 . 0 7

9 . 4 5

9 . 6 1

9 . 8 4

1 0 . 1 6

1 0 . 7 2

1 1 . 9 0

1 3 . 0 6

1 4 . 1 0

1 5 . 1 8

163

I

2A

20 -

16 -E

SL

o in I o 12

8 -

4 -

0

-

-

-

—

-

y\ -PROPYLAMINE

/ / J» ^?^^*^

1 1 1

•,/^

CTAB

1

^ '

^ "

1 1

0-4 0-8 1-2 V6 - 1

C ( m M l )

2-0 2-4

F ig . 4 Plots of K vs. C of C T A B in propylamine

wate r mix tures at d i f f e r e n t propy lamine

concent ra t ions oX SO^C

164

Table 5: CMC values of CTAB, CPC and SDS in amine-water

mixtures at 30 C.

Amine concentration-

(mMl"^)

Ethylamine

CTAB CPC

Propylamine

SDS CTAB

0.00

0.50

1.00

2.00

2.50

5.00

0.92

0.89

0.86

0.72

0.53

0.93

0.66

0.62

0.51

8.10

7.90

7.70

0.92

0.84

0.73

0.59

7.35

1B5

0-5

o E thy lamine

• Propy lamine

0 0-5 1-0 1-5 2-0

Amine concn. (mMl )

2-5

Fig. 5 Va r ia t i on of CMC of C T A B as a

f unc t i on of amine concentrat ion

at 30°C

166

Table 6: Slopes (Ohm" /Ml ) above and below the CMC of

CTAB in amine-water mixtures at 30°C

Amine concentration

(mMl'-'-)

Ethylamine slope

Propylamine slope

Above CMC Below CMC Above CMC Below CMC

0.00

0.50

1.00

2.00

2.50

0.051

0.052

0.048

0.055

0.053

0.19

0.18

0.17

0.17

0.13

0.051

0.054

0.047

0.046

0.19

0.16

0.14

0.14

167

Table 7: Slopes (Ohm' /Ml"''") above and below the CMC of

CPC and SDS in ethylamine-water mixtures at

30°C.

Ethylamine concentration

(mMl*- )

SDS slope

CPC slope

Below CMC Above CMC Below CMC Above CMC

0.00

0.50

1.00

2.00

5.00

0.130

0.126

0.118

0.107

0.045

0.046

0.048

0.048

0.213

0.208

0.192

0.179

0.096

0.100

0.0926

0.0926

DISCUSSION

In discussing the effect of these amines on the CMC

of the surfactants, it must be realized that the observations

are the results of several factors. When a surfactant dissolves

in water, there is not only an interaction between the hydro-

philic portion of the molecules and the water, i.e., hydration,

but a definite role in the change of water structure in their

vicinity is played by the hydrocarbon moiety of surfactant

molecules, which is capable of being accommodated in the

ready-made vacancies, of the structure of water, displacing

the hydrophobic cavity of molecules and shifting the equili­

brium of structural formations. Moreover, the polar charged

portion of the molecules, in the presence of hydration is also

capable of acting upon the surrounding solvent, exerting a

decomposing or stabilizing effect. Naturally, the addition of

a third component (in the present case an amine) in water-

surfactant system will result in the perturbation of the above

mentioned mechanism.

Two theories have been proposed to explain the effects

of organic additives on micelles: one dealing primarily with

the solubilization of organic additives in micelles, put forth

231-233 by Emerson and Holtzer and others . They classified the

additives into nonpenetrating and penetrating categories.

Nonpenetrating additives supposedly affect micelle stability

by altering the dielectric constant of water and by providing

159

hydrophobic contacts for the hydrocarbon chains at the mice-

liar surface. Penetrating additives increase the stability

of the micelle by decreasing the surface charge density

through incorporation of hydrocarbon portion of the additives

227 between surfactant chains just below the micelle surface

The second theory is that additives have a direct effect on

234 the water structure . Structure makers stabilize micelles

while structure breakers have the opposite effect.

A perusal of table 5 indicates that the CMC of CTAB,

CPC and SDS in presence of small concentration of amines have

been reduced considerably in comparison to their values in

pure water. In the light of the present results and previous

discussion the CMC lowering effect of small amount of amines

could be explained as follows: addition of an amine to water

may promote water structuring in its vicinity as in case of

219 235 medivira chain alcohols ' with concomitant increase of

driving force for micelle formation resulting in a lowering

of the CMC and an increase in mice liar size. Vfhen the concen­

tration of amine was increased the conductivity of the solu­

tions decreased. This probably due to the partitioning of

amine into the outer portion of the micelle leading to an

increase in micellar size with the concomitant decrease in

the area per head group, thus increasing surface charge

density of the micelle and increasing the counterion binding

170

236 resulting in a decrease in the conductivity of the system

Table 5 shows that CMC of CPC decreases more than that of

CTAB in presence of same concentration of amine in the system.

This decrease in CMC could be explained on the basis of the fact

that with aromatic pyridiniura salt (CPC) there would be a

delocalization of charge as well as decreased charge shiel­

ding than with the trimethyl salt (CTAB)^ . Both of these

interrelated factors undoubtedly affect interaction with amine

and therefore CMC. Consequently CMC of CPC decreases strongly

in comparison to CTAB in presence of ethylamine. It could also

be seen from table 5 that in the same concentration range the

CMC decreasing effect was greater for propylamine than ethyla­

mine. Figure 5 shows the variation of CMC as a function of

amine concentration in the system. For both the amines the

CMC decreases linearly with the increase in amine concentra­

tion. The rate of CMC decrease (-K) to the concentration of

amine was found just double for propylamine than ethylamine

i.e., 0.17 and 0,08 respectively. Both the observations

indicate that the CMC decreasing effect of amines increases

219 with the chain length of amine as in case of alcohols . This

is possibly due to the fact that the increasing alkyl portion

of the molecule will increase the driving force for association

with the micelle and because the large alkyl groups would tend

to decrease the surface charge density more by causing larger

seperations between the charged head groups. A comparison of

171

232 237 CMC depression rate of SDS by ethylamine and ethanol -"''-"

shows that -K value is hundred times more in ethylamine than

in ethanol. A similar type of behaviour was observed for

CTAB- propylamine and CTAB-propanol system. These observation

may be explained in the light of greater partitioning of

209 * amines than the corresponding alcohols producing higher

perturbation of micelle leading to increased value of K,

The same conclusion may be arrived at by comparing the slopes

of conductance versus concentration plots obtained below and

above CMC (figure 1-4) for CTAB, CPC and SDS in amine-water

mixtures as recorded in tables 6 and 7,

172

R E F E R E N C E S

173

1. Hartley, "Aqueous Solutions of Paraffin Chain Salts",

Hermann etcie, Paris, 1936.

2. J.H. Fendler and E.J, Fendler, "Catalysis in Micellar and

Macromolecular systems," Academic Press, New York 1975,

3. J.K. Thomas, "The Chemistry of Excitation at Interfaces",

American Chemical Society, Washington D.C, 1984,

4. J,W. McBain, "Colloid Science", D.C, Heath and Co,, Boston,

1950.

5. K.J, Mysels, "Introduction to Colloid Chemistry", Inter

Science, Rub, Inc. New York, 1959.

6. M.J. Schick, J, Coll-. Sci, r7, 801 (1963),

7. M.J. Schwuger, JAOCS, 52, 258 (1982).

8. J, Leja, "Surface Chemistry of Froth Flotation", Plenum,

New York, 1982.

9. R.H. Ottewill, in Nonionic Surfactants (M.J. Schick, Ed.),

Dekker, New York, 1967.

10. P. Mukherjee, "Solution Chemistry of Surfactants"

(K.L. Mittal Ed.), Plenxim Press, New York, 1959,

11. T. T^dros, Ed. "Surfactants" Academic Press, New York, 1984

12. B. Lindman and H. Winnerstrom, Top. Cur. Res. 87, 3 (1980).

13. F.M. Menger, J.M. Jerkunica and J.C. Johnston, J, Am. Chef".

Soc. _1£0, 4678 (1978).

174

14. F.M. Menger, H, Yoshinaga, K.S. Venkalusubban and A.R. Das,

J. Org. Chem. 46, 415 (1981),

15. M.A.J. Rodgers, Chem. Phys. Lett, 78, 509 (1981).

16. Idem, J. Phys, Chem, 85, 3372 (1981),

17. P. Fromjerz, Chem, Phys. Lett. 21' 460 (1981).

18. F.M. Menger and D.W, Doll, J, Am, Chem, Soc, 106, 1109

(1984).

19. K.A. Dill, D.E. Koppel, R.S, Cantor, J,D, Dill, D. Bendedouch

and Sow-Hsin Chen, Nature, 309, 42 (1984).

20. K.A. Dill and P.J. Flory, Proc. Natl, Acad, Sci. U.S.A. 77/

3115 (1980); 78, 676 (1981).

21. K.A. Dill, in "Surfactant in Solution", Vol. 1 (K.L. Mittal

and B. Lindman, Eds,), pp, 307, Plenum Press, New York,

1983,

22. F.M, Menger, Nature, 313, 603 (1985),

23. B. Cabane, Nature, 314, 385 (1985),

24. V,M, Mikhal'chuk and A.I. Serdyuk, Geal. Khim. Biol. Nauki.

2, 46 (1983),

25. H. Winnerstrom and B, Lindman, Phys. Report, 5^* 1 (1979).

26. J.H. Fendler, J. Phys. Chem. 84, 1485 (1980).

27. J. H. Fendler, Ace. Chem. Res. 1_3, 7 (1980).

28. J.H. Fendler, in "Membrane Mimetic Chemistry", Wiley Inter

Science, New York, 1982.

1 /o

29. J.H. Fendler, Ace. Chem. Res. 2 , 153 (1976).

30, K. Kon-No, H, Asano and A. Kltahara, Prog, Colloid

Polymer Sci. 68, 20 (1983).

3l". J.B. Peri, J. Colloid Interface Sci. 2^, 6 (1969).

32. M.B. Methews and E. Hirschhorn, J. Colloid Sci. 8, 86

(1953).

33. K. Kon-No and A. Kitahara, J. Colloid Interface Sci.

35_, 636 (1971).

34. P. Stilbs and B. Lindmen, J. Colloid Interface Sci. 92,

290 (1984).

35. C. Biocelli, A.G. Marreello and A.M. Guilani, Appl.

Spectrose. 88, 537 (1984).

36. V.E. Asadchikov, A.L. Sleapakor, N.I, Mishcheuko and A,B,

Sorokin, Khim. Piz. 8, 1138 (1982).

37. M. Boutonnet, J. Kizling, P. Stenius and G. Maire, Coll.

Surfaces, 5, 209 (1982).

38. J.B. Nagy, A. Gourgue, and E.G. Deroune, Stud. Surf. Sci.

Catal., 1982. Preparation of Catalysts, Third International

Symposiiim on Scientific Bases for the Preparation of

Heterogeneous Catalysts, Louvan-La-Neuve, Sept. 1982;

Elsevier: Amsterdam, 1982.

39. M. Gobe, K. Kon<rNo, K. Kandori and A. Kitahara, J. Colloid

Interface Sci. 93, 293 (1983).

176

40. K. Kurihara, J, Kizling, P, Stenius and J.H, Fendler, J,

Am. Chem. Soc. 105, 2574 (1983).

41. Y. Moroi, H, Akisada, M. Saito and R. Matuura, J, Colloid

Interface Sci. 61_, 233 (1977).

42. Y, Moroi, K Motomura and R, Matuura, J. Colloid Interface

Sci, 46, 111 (1974).

4.3, N, Nishikido, Y, Moroi and R, Matuura, Bull, Chem. Soc.

Japan, 48, 1387 (1975).

44. Y. Moroi, N. Nishikido and R, Matuura, J. Colloid Interface

Sci. 5£, 356 (1975).

45. K. Shinoda, T. Nakagawa, B. Tamamushi and T. Isemura,

"Colloidal Surfactant", Academic Press, New York, 1963.

46. K. Shinoda, Bull. Chem. Soc. Japan, 2^* ^^^ (1955).

47. K. Shinoda, J, Phys. Chem. 58, 541 (1954),

48. R.F. Kamrath and E.I. Pranses, J, Phys, Chem. 8^, 1642

(1984).

49. S.N, Wall and C.G. Elvingson, J, Phys, Chem, 89_* 2695

(1985),

50. C. Elvingson and S, Wall, J, Phys, Chem. 90, 5250 (1986),

51. D, Attwood and A.T. Florence, Surfactant Systems, Chapman

and Hall, New York, 1983.

52. W.L. Hinze and D.W. Armstrong, Eds,"ordered Media in Chemical

Separations" American Chemical Society, Washington, 1987.

177

53. D.w. Armstrong, Sep. Purif. Methods, 1£, 212 (1985).

54. W.L. Hinze, in "Colloids and Surfactants: FvundamentaIs

and Applications" (£• Bumi and E, Pelizzetti, Eds.)

Society Chemica Italiana, R<»ne, pp. 167-207, 1987.

55. D.O. Shah and R.S. Schechter, Eds, "Improved Oil Recovery

by Surfactant and polymer Flooding", Academic Press,

New York, 1977.

56. V. Ramamurthy, Tetrahedron Report No. 211, Tetrahedron,

4^, 5753 (1986).

57. Willie L. Hinze, H.N, Singh, Zheng-Sheng Fu, R.W. Williams,

D.J. Kippenberger, M.D. Marries and F.S. Sadek, "Chemical

Analysis of Polycyclic Aromatic hydrocarbons (T. Vo-Dinh

Ed.) John Wiley and Co., Incx New York, 1988.

58. Willie L. Hinze, H.N. Singh, Y. Baba and N.G. Harvey,

TRAC, 3(8), 193. (1984).

59. J.H. Schulman, W. Stoeckinius and L.M. Prince, J. Phys.

Chem. 63, 1677 (1959).

60. T.P. Hoar and J.H. Schulman, Nature (London), 152, 102

(1943).

61. J.H. Schulman and J.B. Montagne, Ann, New York Acad. Sci.

9^, 366 (1961).

62. W. Stoeckinius, J.H. Schulman and L.M. Prince, Kolloid-Z.

uZ. Polymere, 169, 170 (1960).

63. J.H. Schulman and J.A. Friend, J. Colloid Sci. £, 497

(1949).

64. J.H. Schulman and D.P. Riley, J. Colloid Sci. 3_/ 383 (1948)

173

65.. I.A. Zlochower and J.H. Schulman, J. Colloid Interface

Sci. 2A, 115 (1967).

66. C.E, Jr. Cooke and J.H, Schulman, Proc. 2nd Scandinavian

Symp. Surface Activity, Stockholm, November 1964.

67. J.E, Bowcott and J,H, Schulman, Z. Electro Chem, , 283

(1955),

68. J.H. Schulman and T.S, McRoberts, Trans Paraday Soc. 42B,

165 (1946).

69. P.A. Winsor, Trans. Faraday. Soc, 44, 376 (1948),

70. P.A, Winsor, "Solvent properties of Amphiphilic Compo\inds",

pps. 7, 57-60, 68-71, 190^ Butterworths, London, 1954.

71. P.A, Winsor, Chem. Reviews, 68, 1 (1968),

72. W.C. Griffin, J. Soc. Cosmet. Chem. 1, 311 (1949); 5_, 249

(1954).

73. K. Shinoda and H. Kunieda, J. Colloid Interface Sci, 4_2,

381 (1973),

74. K. Shinoda, J, Colloid Interface Sci, 24, 4 (1967).

75. K. Shinoda and H, Saito, J, Colloid Interface Sci, 2^,

70 (1968),

76. H, Saito and K, Shinoda, J, Colloid Interface Sci. 32,

647 (1970).

77. H. Saito and K. Shinoda, J. Colloid Interface Sci. 24,

10 (1967).

173

78. K, Shinoda and T, Ogawa, J. Colloid Interface Sci. 24,

56 (1967).

79. K. Shinoda and H. Takeda, J, Colloid Interface Sci. 3£#

642 (1970).

80. K. Kon-No and A, Kitahara, J, Colloid Interface Sci. 33_,

124 (1970),

81. K. Kon-No and A. Kitahara, J. Colloid Interface Sci. 3£,

221 (1970).

82. K. Kon-No and A. Kitahara, J. Colloid Interface Sci. 32'

469 (1971),

83. K. Kon-No and A. Kitahara, J. Colloid Interface Sci. 41 ,

47 (1972).

84. H.L. Rosano., R.C, Peiser and A, Eydt, Rev. Franc. Corps

Gras, ]^, 249 (1969).

85. H.L. Rosano, J. Soc, Cosmet. Chem. 2^, 609 (1974).

86. H.L. Rosano, T. Lan, A Weiss, J.H. Whittam and W.E.

Gerbacia, J. Phys. Chem. 85, 468 (1981),

87. W. Gerbacia and H.L. Rosano, J. Colloid Interface Sci.

44_, 242 (1973).

88. M.C. Carey and D.M. Small,Am.J. Med. 49, 550 (1970).

89. P. Becher, Emulsions; Theory and Practice, 2nd ed.

Reinhold Pub. Crop. New York pp. 52, 297, 1975.

90. L.I. Osipow, J. Soc. Cosmetic chemists, _1£, 277 (1963).

ISO

91. J.W. McBain and J.J, O'Connor, J. Am. chem. Soc. ^ ,

2855 (1940).

92. H.L. Rosano and G.B. Lyons, J. Phys. Chem. 89, 363 (1985)

93. R. Leung and D.O. Shah, J. Colloid Interface Sci. 120,

320 (1987).

94. K. Shinoda and Y. Shibata, Colloids Surf. 19_, 185 (1986).

95. R.C. Nelson, SPE 8824, first joint SPE/DOE Symposium on

Enhanced Oil Recovery, Tulsa, April 20-23, 1980.

9 5. J.H. Fendler in "Reverse Micelles," Edited by P.L.

Luisi and B.E. Straub, p. 305, Plenum; New York, 1984.

97. L.M, Prince, "Microemulsionsi Theory and Practise",

Academic Press, New York, 1977..

98. D. Langevin in "Reverse micelles". Edited by P.L. Luisi

and B.E. Straub, p. 287, Pleniim, New York, 1984,

99. H.F. Eicke in, "Microemulsions", Edited by I.D. Robb,

Plenum, New York, 1982.

100. K.E. Benett, J.C. Hotfield, H.T. Davis, C.W. Mocosco

and L.E. Scriven, in "Microemulsions", Edited by I.D.

Robb, Plenum: New York, 1982.

101. B. Widom, D.A. Dawson and M.D. Lipkin, Physica A

(Amsterdam), 140, 26 (1986).

102. S.A. Safran, D. Roux, M.E. Gates and D. Andelman, Phys.

Rev, Lett. 57, 491 (1986).

ISl

103. P.G. DeGennes and C. Toupin, J, Phys, Chem, 86, 2294 (1982)

104. K, Shinoda and S, Friberg, Advances in Colloid and

Interface Sci. 4, 281 (1975).

105. S.R. Palit, V.A. Moghe and B. Biswas, Trans Faraday Soc,

5^, 463 (1959).

106. J.W. McBain and M.C. Field, J. Am. Chem. Soc. 5^, 4776

(1933).

107. P.A. Winsor, Proc. 4th International Congress on Surface

Activity, Brussels, Vol. 2, p. 703, 1964.

108. S. Friberg, L. Mandell and M. Larson, J. Colloid Interface

Sci. 22/ 155 (1969).

109. P. Ekwall, J. Colloid Interface Sci. 29_, 16 (1969).

110. P. Ekwall and L. Mandell, Kolloid Z. Uz^ Polymers, 233,

93B (1969).

111. P. Elcwall, L, Mandell and K, Fontell, Mol. Cryst. Liquid

Cryst. 8, 157 (1969).

112. P. Elcwall and P. Solyom, Kalloid Z. Uz. Polymers. 32* 945

(1969).

113. S. Friberg, L. Mandell and K. Fontell, Acta Chem. Scand,

2^, 1055 (1969).

114. S. Friberg and I. Wilton, Am. Perfumer and Cosmetics,

85(12), 27 (1970).

1S2

115. R.L, Reed and R.N, Healy, in "Improved Oil Recovery by

Surfactant and Polymer Flooding", Edited by D.O. Shah and

R.S, Schechter, Academic Press, New York, 1977.

116. J.H. Hedge and G.R. Glinsmann, SPE 54th Annual Technical

Conference and Exhibition (Lasvegas), Paper no. 8324, 1979.

117. S,P, Gupta and S.P. Trushenski, Soc, Pet. Eng, J, 18, 242

(1979),

118. W.H, Wade, J,C, Morgan, R.S. Schechter, J.K, Jakobson and

J.L, Salager, Soc, Pet. Eng, J. 19 , 271 (1979).

119. K.S. Chan and D.O. Shah, J. Dispersion Sci. Technol. 1,

55 (1979).

120. M. Beviere, R, Schechter and W. Wade, J. Colloid Interface

Sci. 81, 266 (1981).

121. A.M. Bellocq, J. Biais, B. Clin, A. Gelvt, P. Lalanne and

B. Lemnceau, J. Colloid Interface Sci. 7£, 311 (1980).

122. J.V. Nieuwkoop and G. Sonei, J, Colloid Interface Sci.

103, 400 (1985).

123. G.J. Glover, M.C. Puerto, J.M. Maerker and E.L. Sandvik,

Soc. Pet, Eng. J. 3, 183 (1979).

124. S.J, Salter, SPE Paper 12026, Presented at the 58th Annaul

technical Conference and Exhibition of SPE, San Francisco,

California, Oct. 1983.

125. J, Biais, M, Berthe, M, Bourrel, B. Clin and P, Lalanne,

J. Colloid Interface Sci, 109, 576 (1986),

183

126. J. Biais, M, Berthe, B. Clin and P. Lalanne, J. Calloid

Interface Sci, 102, 34 (1984).

127. L.P. Prouvost, T, Satoh, K. Sepehmoori and G.A. Pope,

SPE Paper 13031/ presented at the 59th Annual Technical

Conference and Exhibition of SPE, Houston, Texas,

September 1984,

128. J.L. Salager, E, Vasquez, J.C. Morgan, R.S. Schechter

and W.H. Wade, Soc. Pet. Eng. J. 1^, 107 (1979).

129. L.E, Scriven, in "Micellization, Solubiization and

Microemulsions", Ed, by K.L. Mittal, Plenum Press,

New York, Vol II, 77, 1977.

130. L. Auray, J,P. Cotton, R, Ober and C, Toupin, J. Phys.

Chem. 88, 4586 (1984).

131. L. Auray, J.P. Cotton, R, Ober and C. Toupin, J, Phys.

(Lesulis, Pr.) 4_5, 913 (1984), Physica B (Amsterdem)

136B, 281 (1986).

132. G.A. Pope and R.C, Nelson, Soc. Pet, Eng. J. 5, 339 (1978).

133. R.C. Nelson and G.A. Pope. Soc. Pet. Eng, J. 5, 325 (1978),

134. J. Meunier and D, Langevin, J. Phys. Lett. 43_, L-185(1982).

135. H. Kunieda and K. Shinoda, J. Colloid Interface Sci. 70,

577 (1979),

136. B. Bedwell and E. Gulari, J, Colloid Interface Sci. 102,

88 (1984).

184 137. K. Shinoda, H. Kunieda, T. Aral and J.H. Saijo, J. Phys.

chem. 88, 5126 (1984).

138. Y. Barkat, L.N. Porthney, C. Lalanne-cassou, R.S.

Schechter, W.H. Wade, U, Weerasooriya and S.H. Yiv, Soc.

Pet. Eng. J. , 913 (1983).

139. M. Bourrel, J.L. Salager, R.S. Schechter and W.H. Wade

J. Colloid Interface Sci. Jl' ^^l (1980).

140. S.J. Salter, in "Influence of Type and Amo\mt of Alcohol

on Surfactant-Oil-Brine Phase Behaviour and Properties",

SPE Preprint 6843.

141. A. Gracia, L.N. Portney, R.S. Schechter, W.H. Wade and

S, Yiv, Soc. Pet. Eng. J. 22_, 743 (1982).

142. M. Bourrel and C. Chambu, in "The Rules for Achieving

High Solubilization of Brine or Oil by Amphiphilic

Molecules", SPE Reprint 10676.

143. S.H. Yiv, R. Zana, W. Ulbricht and H. Hoffmann. J.

Colloid Interface Sci. 80, 224 (1981).

144. M. Abe, D. Schechter, R.S, Schechter, W.H. Wade, U.

Weerasooriya and S. Yiv, J. Colloid Interface Sci. 114,

342 (1986).

145. D.O. Shah, R.D. Walker, W.C. Hsieh, N.J. Shah, S. Dwivedi,

J. Nalender, R. Pepinski and D.W. Deamer, "Improved Oil

Recovery Symposium", SPE Reprint 5815. Tulsa, 1976.

185

146. D.O. Shah, V.K. Bansal, K. Chan and W.C, Hsieh, in "ImproveG

Oil Recovery by Surfactant and Polymer Flooding"^ Edited

by D.O. Shah and R.S. Schechter, pp. 293-337, Academic

Press, New York, 1977.

14 7. M, Clausse,C, Boned, J. Peyrelasse, B, Lagourett, V.E.R,

McClean and R.J, Sheppard, in "Surface Phenomena in Enhanc^

Oil Recovery", Edited by D.O,, Shah, pp. 194-228, Plenum

Press, New York, 1981.

148, S. Kirkpatric, Rev. Mod. Phys. 45, 574 (1973).

149, R. Landaver, J. Appl, Phys. 23 / 779 (1952).

150, s. Friberg and I. Burasczenska, Prog, Colloid Polymer

Sci., 62, 1 (1979).

151, R.L. Venable and D,M, Viox, J, Dispersion Sci, Technol.

5, 73 (1984),

152, R,L, Venable, K,L, Elders and J, Pang, J. Colloid Interface

Sci. 1^, 330 (1986) .

153, G, Gillberg, H, Lehtinex and S, Friberg, J, Colloid Inter­

face Sci, 3J.# 40 (1970),

154, L,M. Prince, J. Colloid Interface Sci. 52 , 182 (1975) ,

155, D.O. Shah and R,N, Hamlin Jr,, Science, 171, 483 (1971).

156, F,M, Menger, G, Saito, G.V. Sanzero and J.R. Dodd, J. Am,

chem, Soc, £7, 909 (1975).

157, D.O. Shah, A. Tamjeedi, J.W. Falco and R.D, Walker Jr.,

AIChEJ 18, 1161 (1972); D,0, Shah, Ann, N,Y, Acad, Sci,

204, 125 (1973); J.W, Falco, R,D. Walker, Jr., and D.O,

Shah, AIChEJ 2_0, 510 (1974).

186

158. H.N. Singh, Shanti Swarup, R.P, Singh and S.M. SE? - ' i,

Ber. Btinsenges, Phys. chem. 82# 1115 (1983).

159. Sanjeev K\imar, Surendra Singh and H.N, Singh, J. Sv.:ic,

Sci. Technol. 2(2), 85 (1986).

160. K. Kojikano, T, Yamaguchi and T. Ogawa, J. Phys. cb' m.

88, 793 (1984),

161. B. Lindman, P. Stilbs and M.E. Moseley, J. Collo, '. I.-'-or-

face Sci. 83, 569 (1981).

162. P.G, Nilson and B. Lindman, J, Phys. chem. 87, 47L " '...' ..

163. W.I. Higuchi and J. Misra, J. Pharm. Sci. , 455 (1962).

164. S.G. Frank and G. Zografi, J. Colloid Interface Sci. i*

28 (1965).

165. V.K. Bansal, K, Chinnaswamy, C. Ramchandran and D.O. Shah,

J. Colloid Interface Sci. 72_, 524 (1979).

166. B.W. Ninhara, S.J. Chen and O.F. Evans, J. Phys. chem. 8^

5855 (1984).

167. B.H. Robinson, C. Toprakcioglu and J.C. Dore, J. chem.

Soc. Faraday Trans. 8£, 13 (1984).

168. P. Lianos, J. Lang, C. Strazielte and R. Zana, J. ".

chem. 88, 819 (1984).

169. M. Clausse, L. Nicolas-Morgantini, A, Zradba and D Touraud.

in "Microemulsion systems". Edited by H.L. Rosaro c..d

M. Clausse, Marcel Dekker, Inc. New York,(1987).

170. R.S. Stems, H. Oppenheimer, E. Simon and W.D. Harkins,

J. chem. Phys. 15, 496 (1947).

1S7 171. H.B. Klevens, chem. Rev. 42, 1 (1950).

172. R.L. Venable and D.A. Weingaertner, J. Dispersion Sci.

Technol. £, 425 (1983).

173. R.L. Venable, JAOCS, 62,(1), 128 (1985).

174. E, RucXenstein and J. Chi, J. chem. Soc, Faraday Trans,

ii, 1690 (1975).

175. C. Wegner, Colloid and Polymer Sci. 254, 400 (1976),

176. G.S. Hartley, Trans. Faraday Soc* 32* 130 (1941).

177. E. Ruckenstein, Fluid Phase Equilibrixim, 20, 189 (1983).

178. V.K. Bansal, D.O, Shah and J.P. O'connell, J. Colloid

Interface Sci. 25# 462 (1980).

179. C.T. O'Conski, J. Phys. Chem. 64, 605 (1968).

180. surendra Singh,in Ph.D. Thesis, Aligarh Muslim University,

Aligarh, India, 1986.

181. S.L. Holt, J, Dispersion Sci. Technol. 1, 423 (1980).

182. P. Stilbs, K. Rapacki and B. Lindroan, J. Colloid Interface

Sci. 95, 583 (1983),

183. J. Lang, R. Rueff, M. Dinh-Cao and R. Zana, J. Colloid

Interface Sci. 101, 184 (1984).

184. s. Friberg, I. Buraczewska and G. Gillberg, J. Colloid

Interface Sci. 56, 19 (1976).

185. L.E. Scriven, Nature, 263, 123 (1976).

188

186. C.E. Blevins, G.P. Willhite and M.J. Michnick, SPE 82G0,

54th Annual Fall Technical Conference and Exhibition of

the Society of Petroleuun Engineers of AIME« Las Vegaa,

September 23-26, 1979.

187. J.G. Dominguez, G.P. Willhite and D.W, Green, in

"Solution Chemistry of Surfactants" (Edited by K.L.

Mittal) vol. 2, pp. 673, Academic Press, New York, 1979.

188. A, Zradba and M. Clausse, Colloid Polymer Sci. 262, 754

(1984).

189. M. Clausse, A. Zradba and L.C.R. Nicolas-Morgantini,

Acad. Sci. Paris 296, Ser. II, 237, 1983.

190. J.L. Finney, Nature, 266, 309 (1977),

191. K. Gunther and D. Heinrich, Z. Physik. 185, 345 (1965).

192. E.W. Kaler and S. Prager, J, Colloid Interface.Sci.86,359 (1982).

193. K.J. Lissant, in Emulsions and Emulsion Technology,

Surfactant Science Series,

Vol. VI, M.J. Schick and F.M. Fowkes (Eds), Marcel

Dekker, New York, Part 1, Chap 1, pp. 1-69, 1974.

194. S.J. Chen, D. Fennelll Evans and B.W. Ninham, J. Phys.

Chem. 88, 1631 (1984).

195. A.C. Mark, R. Nagrajan and E. Ruckenstein, J. Colloid

Interface Sci. 9^, 168 (1984).

196. Y. Talmon and S. Prager, J. Chem. Phys. 69, 2984 (1978^.

182

197. J. Van Nieuwkoop and G. Snoei, J, Colloid Interface fci.

103, 417 (1985).

19a. A.N. Bellocg, J. Blals, B. Clin, P. Lalanne and B.Leruan-

ceau, J. Colloid Interface Sci, 70, 524 (1979).

199. S.E, Friberg and R.L. Venable, in "Encyclopedia of

Emulsion Technology" Edited by P. Becher, 1, 287,

Dekker, New York, 1983.

200. E. Sjoeblon and U. Henriksson, Proc, 4th Int. Symp.

Surfactant in solution, 3^, 1967, 1984.

201. P. Mukerjee and K.J. Mysels, "Critical Micelle Concen­

trations of Aqueous Surfactant Systems", NSRDS-NBS (U.S.)

36, Washington, D.C., 20402, 1971.

202. A. Seidell "Solubilities of Organic Ccmipoxinds", Vol.11,

1941.

203. A. Veis and C.W. Hoerr, J. Colloid Sci. 41 , 343 (1960).

204. GanzuoLi, Xianglong Kong and Rong Guo, Sixth Int. Symp.

Surf. Sol. paper No. ME-11, PP. 150, 1986. 205. K.S. Birdi, Colloid and Polymer Sci. 260, 628 (1982).

206. R. zana, in "Surface Phenomena in Enhanced Oil Recovery",

Edited by D.O. Shah, Plenum, New York, 1980.

207. A Skoulios and D, Guillon, J. Phys. Lett. , L-137

(1977).

208. J. Pang and R.L. Venable, J. Colloid Interface Sci. 116,

269 (1987).

209. K.R. Wormuth and E.W. Kaler, J. Phys. Chem. 91_, 611(1987)

190

210. S. Gupta and S. Sharma, J. Ind. Chem. Soc. 42* 85."" (1' '")

211. R. Bakeeva, S. Pedorov, L, Kudryavtseva, V, Bel'skii

and B. Ivanov, Kolloidn.Zh, 46, 755 (1984)*

212. R. Laughlin, Adv. Liq. Cryst. 3,, 41 (1978).

213. S.I. Ahmad, K. Shinoda and S. Priberg, J. Cox., .3

Interface Sci. £7, 32 (1974).

214. J. Desnoyers, P. Quirion, D. Hetu and G, Pertcn, C«=»n. J,

Chem. Eng. 61., 672 (1983).

215. S.J. Chen, D.P. Evans and B.W. Ninham, J. Ph^^), -.;hem.

88, 1631 (1984).

216. R. Zana, J. Colloid interface Sci. 78, 330 (1930).

217. P. Lianos and R. Zana, J, Colloid Interface Scio 84,

100 (1981).

218. M. Manabe and M. Koda, Bull. Chem. Soc. Japa:;, 51, .S"

(1978).

219. H.N. Singh and Shanti Swarup, Bull. Chem. Soc. Japan,

5i, 1534 (1978).

220. M. Manabe, M. Koda, and K. Shirahama, QT, Coll'- * T er-

face Sci. 77, 189 (1980).

221. H.N. Singh, R.P. Singh, S.M. Saleem and K.S. irr*!,

84, 2191 (1980).

222. R. Zana, S. Yiv, C. Strazielle and P. Lianos, .J. rr loid

Interface Sci. 80, 208 (1981).

191

223. David Oakenfull, J. Colloid Interface Sci. 88, 532

(1982).

224. R, Zana, C. Picot and R. Duplessix, J. Colloid Interface

Sci. 93./ 43 (1983).

225. P.H. Kothwala, T.N, Nagar and P. Bahadur, Coiloids and

Surfaces, !£, 2191 I19bb).

225. R. Leung and D.O. Shah, J. Colloid Interface Sci. 113,

484 (1986).

227. I.V. Rao and E. Ruckenstein, J. Colloid Interface Sci.

113, 375 (1986).

228. N.R. Jagannathan, K. Venkateswaran, P,G. Herring,

G.N. Patey and D.C. Walker, J. Phys. Chem. 91, 4553

(1987).

229. L. Magid, in "Solution Chemistry of Surfactants", Edited

by K.L. Mittal, Vol. 1, p. 427, Plenum, New York, 1979.

230. K. Hayase and S. Hayano, J. Colloid Interface Sci. 63 ,

446 (1978).

231. M.F. Emerson and A. Holtzer, J. Phys, Chem. TjL ' 320

(1967).

232. K. Shirahama and T. Kashiwabara, J. Colloid Interface

Sci. 3^, 65 (1971).

233. A.S.C, Lawrence and J.T. Pearson, Trans Farada. =0 .

63, 495 (1967).

192

234. W.U, Malik, S.P, Verma and P. Chand, Indian J,

Chem. 8, 826 (1970).

235. A Ben-Nairn and M. Yaacobi, J. Phys. Chem. 78, 170

(1974).

236. C. Tanford, J. Phys. Chem. 76, 3020 (1972).

237. M. Manabe and M. Koda, The Memoirs of the Niihama

Technical College, l^, 57 (1977).