Block 2

Polymerization and Polymer Reactions

Pedro Teixeira Gomes

A Classical Methods

1- Non-vinyl Polymers

2- Vinyl and Acetylenic Polymers

Polymer Synthesis

2- Vinyl and Acetylenic Polymers

•Radical Polymerization and Copolymerization •Cationic and Anionic Polymerization •Coordination Polymerization•Chemical Reactions in Vinyl Polymers

B Modern Methods

•Coordination Polymerization (Metallocenic and Post-Metallocenic)•Controlled/Living Polymerization

BIBLIOGRAPHY

- M. P. Stevens, "Polymer Chemistry - An Introduction", 3rd ed., Oxford Univ. Press, 1999 (DEQ Library: 2 nd ed., 1990)

- G. Odian, “Principles of Polymerization”, 4th ed., Wiley-Interscience, N.Y., 2004(Pedro T. Gomes’ office)

- M. Fontanille, Y. Gnanou, “Chimie et Physico-chimie des Polymères“, Dunod, Paris, 2002.

Livros Gerais

- F. Billmeyer, "Textbook of Polymer Science", Wiley-Interscience, 3rd ed., N.Y., 1984.(DEQ Library )

- “Encyclopedia of Polymer Science and Technology”, 3rd ed., Wiley-Interscience, 2004 (DEQ Library )

- M. Michalovic, K. Anderson, L. Mathias, “The Macrogalleria”, site do Polymer Site LearningCenter (da University of Southern Mississippi) (http://www.pslc.ws/macrog.htm)

POLYMER SYNTHESIS – POSSIBLE ROUTES

• STEP_GROWTH POLYMERIZATION(Polycondensation)

- Applied to NON-VINYL MONOMERS

• CHAIN POLYMERIZATION (Polyaddition)

• CHEMICAL MODIFICATION OF EXISTING POLYMERS or COPOLY MERS

- Applied to VINYL MONOMERS- Applied to some POLYESTERS and POLYAMIDES obtained by Ring Opening Polymerization

Block 2

Non-Vinyl Polymers

Pedro Teixeira Gomes

• STEP-GROWTH POLYMERIZATION OF NON-VINYL MONOMERS

SYNTHESIS OF NON-VINYL POLYMERS – POSSIBLE ROUTES

• CHAIN POLYMERIZATION OF RING OPENING POLYMERIZATION OFHETEROCYCLIC MONOMERS

STEP-GROWTH POLYMERIZATION (2 ROUTES)

• 1 HETERO-BIFUNCTIONAL MONOMER (A-B)

n A B A Bn

EX: AMINOACID

Aminoundecanoic acid NYLON 11

CH2H2N C

O

OH

n10

- 2n H2OCH2NH C

10

O

n

EX: DICARBOXYLIC ACID and DIAMINE

NYLON 66Adipic Acid Hexamethylenediamine

CH2C C

O

OH

O

HO

n4

+-2n H2O

CH2C C4

O O

NHn

CH2H2N NH2n6

CH2 NH6

• 2 HETERO-BIFUNCTIONAL MONOMERS (A-A and B-B)

n A A A A Bn

n B B+ B

STEP-GROWTH POLYMERIZATION

%CONV DP(monomer)

0% 0

EX: DICARBOXYLIC ACID and DIAMINE

NYLON 66Adipic Acid Hexamethylenediamine

CH2C C

O

OH

O

HO

n4

+-2n H2O

CH2C C4

O O

NHn

CH2H2N NH2n6

CH2 NH6

50% 2

75% 2,25

100% 3

(schematic only; not quantitative)

0% 0

CHAIN POLYMERIZATION

CH

Cln CH

Cl

CH2n

CH2

EX: VINYL CHLORIDE

Vinyl Chloride PVC

%CONV DP(monomer)

0% 0

50% 6

75% 9

100% 12

(schematic only; not quantitative)

•••• EACH MONOMER MOLECULE HAS 2 FUNCTIONAL GROUPS

No = initial number of functional groups

Co = initial concentration of functional groups

EQUIMOLAR REACTION

The total number of functional groups of the type A-A or B-B (or initial concentration of monomers),When the mixture is equimolar is:

o oo

oo

oN N C C(ou C )

2 2 2N

2+ = + =+ = + =+ = + =+ = + =r

2 2 2 2

•••• EACH POLYMER MOLECULE ALSO HAS 2 FUNCTIONAL GROUPS

N = number of functional groups at time t

C = concentration of functional groups at time t

The total number of polymer chains (or polymer concentration) at time t is:

N N C C(ou )

2 2 2N C

2+ = + =+ = + =+ = + =+ = + =r

o on

N CDP

N C= == == == =

The average number of monomer units per polymer chain at time t – DPn – is:

o o

o o

N N C Cp

N C− −− −− −− −

= = == = == = == = =CONVERSION

Substituting in DPn expression:

n1

DP1 p

====−−−− CAROTHERS EQUATION

1 p−−−−

% Conversion p DPn MW* of NYLON-6,6

50 0.500 2 226

75 0.750 4 452

90 0.900 10 1130

99 0.990 100 11300

99,8 0.998 500 56500

99,9 0.999 1000 113000

* MW = DP n ×CH2C C

4

O O

NH CH2 NH6

2

113

CAROTHERS EQUATION

n

URnn UR

1DP

1 p

MM M DP

1 p

====−−−−

= × == × == × == × =−−−−0

50

100

150

0 0.25 0.5 0.75 1

conversão (p)

Mnx

10-3

conversion

STEP-GROWTH SCHEME:

Monomer + Monomer DimerDimer + Monomer TrimerDimer + Dimer TetramerDimer + Trimer Pentamer (…etc.)Trimer + Monomer TetramerTrimer + Dimer Tetramer

IN GENERAL :

n-mer + m-mer (n+m)-mer

......

n n+-2n H2O

NH2H2N C C

O

OH

O

HO

C C

O

n

O

NHNH

• CONDENSATION (Examples)

n n+-2n H2O

OHHO C C

O

OH

O

HO

C C

O

n

O

OO

Polyesters

Polyamides

CO O

O

HO OH C

O-2n HCl

STEP-GROWTH POLYMERIZATION

Polycarbonates

COn

OHO OHn n+ C

Cl Cl

-2n HCl

CNHn

NH

O

H2N NH2n n+ C

O

Cl Cl

-2n HCl

Polyureas

Phenol-Formaldehyde Resins

• PSEUDO-CONDENSATION (Examples)

Polyurethanes

OOn

CNH NHC

OO

N N n OHHOCCO On +

NHNHn

CNH NHC

OO

N N n NH2H2NCCO On +

Polyureas

POLYCONDENSATION CARBOXYLIC ACID DERIVATIVES

ORGANIC CHEMISTRY REACTIONS USED IN THE SYNTHESIS O F:

R C

O

OH

+ R'OH R C

O

OR'

+ H2O

R C

O

OR''

+ R'OH R C

O

OR'

+ R''OH

DIRECT ESTERIFICATION(ALCOHOLYSIS)

TRANSESTERIFICATION

PO

LYE

ST

ER

S

OR'' OR'

R C

O

Cl

+ R'OH R C

O

OR'

+ HCl REACTIONS OF ACYLCHLORIDE WITH ALCOHOLS

REACTIONS OF ANHYDRIDESWITH ALCOHOLS

PO

LYE

ST

ER

S

R C

O

O + R'OH R C

O

OR'

+

C

O

R

R C

O

OH

R C

O

OH

+ R'NH2

ESTERAMINOLYSIS

R C

O

OR''

+ R'NH2 R C

O

NR'H

+ R''OH

PO

LYA

MID

ES

saltdehydration

DIRECT AMIDATION

Isolation forStoichiometric

Control

R C

O

O- +NRH3

∆∆∆∆+ H2OR C

O

NRH

Acid-Base Reaction

REACTIONS OF ANHYDRIDESWITH AMINES

OR'' NR'H

R C

O

Cl

+ R'NH2 R C

O

NR´H

+ HCl

•••• POLYESTERS - POLYESTERIFICATION

EXAMPLE: • POLY(ETHYLENE TEREPHTHALATE) (PET; Poly(oxyethylenoxyterephthaloyl) (IUPAC))

ethyleneglycol terephthalic acid PET

CH2

HOn CH2

OH+ C C

O

OH

O

HO

-2n H2OO CH2 CH2 On C

O

C

O

n

POLYCONDENSATION CARBOXYLIC ACID DERIVATIVES

- Main polymer of the polyester textiles (textile fibres) (45%)- Beverage bottles (53%)- Engineering plastic (construction of precision moulds for electric

and electronic devices, etc.)

INDUSTRIALLY : Terephthalic acid is very insoluble and has a high Tm (Tsublim = 300 ºC).

In many cases the dimethyltherephthalate (DMT) (Tfusão = 140 ºC) is used.

+C C

O

OCH3

O

H3CO

2 C C

O

OCH2CH2OH

O

HOH2CH2CO

HOCH2CH2OH + 2 CH3OH

INDUSTRIAL SYNTHESIS OF PET

ethyleneglycolDimethylterephthalate (DMT) bis-(2-hydroxyethyl)terephthalate

∆∆∆∆

T = 150 - 210 ºC

Step 1 - Transesterification

Continuouslydistilled

STEP 2 –∆∆∆∆T = 270 - 280 ºC

IN 2 STEPS – eliminates the necessityof a rigorous 1:1 stoichiometric control

OCH2CH2OC

O

C

O

n

+

(n-1) HOCH2CH2OH

STEP 2 –PolycondensationP = 0.5 – 1 torr

PET

Continuously evaporated

It prevents transesterification reactions withthe polymer (that induce a decrease of Mn)

+C C

O

OCH3

O

H3CO

H2C2 CH2

O

ethylene epoxide

Japanese process

INDUSTRIAL SYNTHESIS OF PET

SYNTHETIC ALTERNATIVE FOR POLYESTERS

• RING OPENING POLYMERIZATION OFCYCLIC ESTERS (LACTONES)

O O (CH )C

O

O O

Chain Polymerization, with acid or basic catalysis

(CH2)x

CO

OZ+

O CH2 C

O

etc.

(CH2)x

CO

CH2O Cx

O

nZ

lactonePolyester

A) EQUILIBRATED REACTIONSthe removal of product (H2O or ROH) is required to shift the equilibrium tothe right and obtain polymers with high Mn (thermodynamic limitation)

DRAWBACKS OF THE POLYESTERIFICATION REACTION

B) NEED OF CATALYSISgenerally, it is required the use of acid or basic catalysts to increase thereaction rate (kinetic limitation)

•••• POLYAMIDES - POLYAMIDATION

EXAMPLE: • NYLON 66 (Poly(hexamethylene adipamide); poly(iminoadipoyliminohexane-1,6-di-yl) (IUPAC))

STEP 1 – Acid-Base Reaction

adipic acidhexamethylenediamine “Nylon Salt” isolated and purified

(exact stoichiometry)

CH2C C

O

OH

O

HO

n4

+ CH2NH2 NH2n6

CH2C C

O

O-

O

-O

n4

CH2H3N+ +NH3

6

CH2C C4

CH2 NH6

O

NH

O

n

+

(2n-1) H2O

NYLON 66 (Tm= 260 ºC)

STEP 2 –Salt Dehydration

∆∆∆∆T = 210 - 280 ºCP = 17 bar (H2O

vapour)

- It excludes O2

- It prevents salt precipitation andsubsequent precipitation on the walls andon the heat transfer surfaces.

- Fibres (60%)- Main engineering plastic

INDUSTRIAL SYNTHESIS OF NYLON 66

SYTHETIC ALTERNATIVE FOR POLYAMIDES

• RING OPENING POLYMERIZATION OFCYCLIC AMIDES (LACTAMS)

- Textile fibres-Engineering plastic

(Tm = 223ºC)

εεεε-caprolactam Poly(εεεε-caprolactam) ≡ NYLON 6 ≡ Poly(imino(1-oxahexamethylene)) (IUPAC)

NH

O

CH2NH C5

O

n

H2O (H+) (B-)

Essentially, Chain Polymerizationinitiated by H2O, by acids or bases.Step-Growth Polymerization (heterobifunctional) is minor but it determins DPn.

εεεε-caprolactam Poly(εεεε-caprolactam) ≡ NYLON 6 ≡ Poly(imino(1-oxahexamethylene)) (IUPAC)

NH

O

NH

OH

NH

OH

H+

NH2

OHN

O

N

O

CH2C NH35

O

CH2NH C5

O

n

H2O (H+) (B-)

HN

O

(n-2)

• POLYAMIDES FROM DE AMINOACIDS(with more than 6 carbons in the amine and acid functional groups)

Aminoacids are heterobifunctional monomers

aminoundecanoic acid NYLON 11

(RILSAN 11)

CH2H2N C

O

OH

n10 - 2n H2O

CH2NH C10

O

n

∆∆∆∆

CH2H2N C

O

OH

nx

x = 3 ou 4

x ≥ 5

x ≤ 2

(CH2)x

CO

NH + H2O

CH2NH Cx

O

n

aminoacid

lactam

nylon x+1

•••• In 3- or 4-membered rings there is ring strain

CYCLIZATION REACTIONS

Along with the chain growth there is a reaction that competes with it :

Chain Cyclization

•Thermodynamics prefers the formation of 5- or 6-membered rings very stable

•••• In 8- to 13-membered rings there is conformational limitations (entropic limitation)

CH2 NHCx

O

HC

O-

N(CH2)

CH2 NHCx

O

Hx

+

Ex:

Do not ring openpolymerise

valerolactam

valerolactone

O

C

NH

C

O

O

X

X

CHARACTERISTICS OF POLYAMIDATION REACTION

A) REACTIONS WITH A MORE NEGATIVE ∆∆∆∆G THAN IN POLYESTERIFICATION the equilibrium is more shifted to the right owing to the high basicity andnucleofilicity of the amine groups (thermodynamically the process is more favourable)

B) REMOVAL OF THE ELIMINATED MOLECULES IS LESS CRIT ICAL

C) NO NEED OF CATALYSIS(kinetically more favourable)

B) REMOVAL OF THE ELIMINATED MOLECULES IS LESS CRIT ICALthan in polyesterification owing to the latter reason, and therefore transesterification reactions, which decrase Mn, are less likely to occur

STEP-GROWTH POLYMERIZATION KINETICS

No = initial number of carboxyl functional groups (C) = total number of monomers C-C and A-A

N = number of carboxyl functional groups (C) at time t

[C]o = initial concentration of carboxyl functional groups (C)

[C] = concentration of carboxyl functional groups (C) at time t

REACTION RATE ( with acid catalysis) Equal reactivity of functional groups is assumed, independently of the value of DPn

EQUIMOLAR REACTION - [C] = [A]

d[C]k ' [C][A]

dt− =− =− =− = k ' k [H ]++++====

2d[C]k ' [C]

dt− =− =− =− =

o

1 1k ' t

[C] [C]− =− =− =− =

n oDP 1 k ' [C] t= += += += +o on

N [C]DP

N [C]= == == == =Since

n oDP 1 k ' [C] t= += += += +

NOTES:

In practice, the reaction is heated gradually until its end

•••• It takes approximately 100 times longer to achieve DPn = 100 than DPn = 2

(although this represents 50% of monomer conversion)

•••• This expression does not take into account the reaction is reversible

In practice, for the polyesterification case, the product eliminated (H2O, ROH, HCl)

is continuously removed as it is formed

REACTION RATE ( without acid catalysis)

2d[C]k [C] [A]

dt− =− =− =− =

Equal reactivity of functional groups is assumed, independently of the value of DPn

In polyesterification drastic conditions (high temperatures and pressures)

sometimes an acid catalyst may be adverse (for example, it may cause

discoloration or degradation of the monomer).

In the absence of catalyst, it is the carboxylic acid that plays the role of catalyst:

EQUIMOLAR REACTION - [C] = [A]

3d[C]k [C]

dt− =− =− =− = 2 2

o

1 12 k t

[C] [C]− =− =− =− =

2 2n oDP 1 2 k [C] t= += += += +

o on

N [C]DP

N [C]= == == == =Since

The increase of DPn is less pronounced than when using an acid catalyst

•••• Both relationships deviate from linearity at low degrees of conversion (<80%)

of functional groups (effect of higher polarity of the medium at low reaction times

induces a decrease in the rate).

n oDP 1 k ' [C] t= += += += +

2 2n oDP 1 2 k [C] t= += += += +

•••• At high degrees of conversion(> 93%), the increase in viscosity prevents an

effective removal of water, leading to an increase in the reverse reaction and,

consequently, to a new deviation in the uncatalyzed reaction. This deviation is not

usually observed in the catalyzed reaction.

n oDP 1 k ' [C] t= += += += +2 2n oDP 1 2 k [C] t= += += += +

MOLECULAR WEIGHT CONTROLIN STEP-GROWTH POLYMERIZATION

on

N1DP

1 p N= == == == =

−−−−

When p ~ 1 (total conversion of functional groups) then:

nDP → ∞→ ∞→ ∞→ ∞

In some step-growth polymerizations there is a need to limit the molecular weight,because the applications of some of the corresponding polymers so require:

•••• COOLING OF THE REACTION MIXTURE

• ADJUSTMENT OF THE STOICHIOMETRIC IMBALANCE(so that one of the reagents is in excess)

• ADDITION OF A MONOFUNCTIONAL REAGENT

M n CONTROL

In a mixture, let us consider there is an excess of monomer B-Bin relation to monomer A-A:

o oABN N>>>>

Initial number of functional groups B Initial number of functional groups A

Defintion of a stoichiometric imbalance(r):

NoA

oB

Nr

N==== (r 1)≤≤≤≤

Each molecule of A-A reacts stoichiometrically with a molecule of B-B:

In these conditions DPn is now given by:

n1 r

DPr 1 2rp

++++====+ −+ −+ −+ −

n1 r

DPr 1 2rp

++++====+ −+ −+ −+ −

Depending on the reaction system we have now the following type of situations:

•••• If r = 1, this equation reduces to the Carothers equation:

• When monomer A-A is totally consumed in the polymerization reaction (p=1), the maximum degree of polymerizationis given by:

n A A A AB Bm B B+ B AB A B B (m-1) B B+

(((( )))) o oB An

max o oB A

C C1 rDP

1 r C C

++++++++= == == == =− −− −− −− −

n A A A AB Bn

m B B+ B AB A B B (m-1) B B+

• When a monofunctional agentis added, r is redifined:

oA

o oB B'

Nr

N 2 N====

++++oA

o oB B'

C

C 2 C====

++++

Monofunctional agent

oA

o oB B'

Nr

N 2 N====

++++

Ex: In the synthesis of NYLON 66, acetic acid(1% molar) is added to limit the molecular weight

It is more practical than controlling the purity, t ime, temperature, viscosity, etc.

n A A A AB Bn

n B B+ B Bx+ B

Monofunctional agent

•••• In heterobifunctional monomers (A-B):

The molecular weight is controlled by the addition of a monofunctional agent

oA

o oB B'

Nr

N 2 N====

++++ o oA BN N====

Monofunctional agent

The previous expression is now valid for o oA BN N====

[A] o = initial concentration of functional groups A

[A] = initial concentration of functional groups A at time t

[B]o = initial concentration of functional groups B

[B] = initial concentration of functional groups B at time t

STEP-GROWTH POLYMERIZATION KINETICS

REACTION RATE ( with acid catalysis)

d[A]k ' [A][B]

dt− =− =− =− = k ' k [H ]++++====

d[A]k ' [A][B]

dt− =− =− =− =

o

o o o

[A] [B]1ln k ' t

[B] [A] [B] [A]

==== −−−−

Thus

= o

o

[A]r

[B]and and o o[A] [A] [B] [B]− = −− = −− = −− = −

o[B]

ln ln r (1 r) [B] k ' t[A]

= + −= + −= + −= + −

NON-EQUIMOLAR REACTION - [B] > [A]

MOLECULAR WEIGHT DISTRIBUTION

It was derived by Flory, through a statistical and probabilistic approach based on theconcept of equal reactivity of the functional groups (applicable to polymerizations ofmonomers A-A and B-B or to the polymerizations of monomers A-B).

xi = molar fraction of chains containing i repeating units (DP = i)

N = total number of molecules that are present at time t

mi = mass fraction of chains containing i repeating units

p = conversion

i 1ix N p (1 p)−−−−= −= −= −= − 2 i 1

im i (1 p) p −−−−= −= −= −= −

Flory or Flory-Shulz or Shulz-Flory distribution

URn

MM

1 p====

−−−−n

1DP

1 p====

−−−−Since

URw

M (1 p)M

1 p++++====

−−−−

w

n

M(1 p)

M= += += += +

BRANCHING. GEL POINT. TRIDIMENSIONAL STRUCTURES

If the monomers have more than 2 functional groups BRANCHING

Ex: Polycondensation of Phthalic Anhydridewith Glycerol (molar ratio 3:2)

O

OH

In case many trifunctional molecules are presentenormous macromolecular networkscan be obtained

O

O

+3 2 HO CH2 CH CH2 OH

phthalic anhydride

glycerol

FUNCIONALITY: f=2

FUNCIONALITY: f=3

3 2 2 3f 2,4

3 2× + ×× + ×× + ×× + ×= == == == =

++++(functions/monomer)

i ii

ii

n f

fn

====∑∑∑∑

∑∑∑∑

average functionality

ni = stoichiometric coefficient

• During polycondensation, macromolecules containing trifunctional monomers in itsskeleton , now have 3 active ends, which grow faster than those containing 2 active ends

• Conversely, theprobability to add other molecules with 3 ends is higher and the growthis even faster. Thus, Mw/M n will increase

• A point will be reached, when the large molecules condense, an infinite network will be formed

GEL POINT

Thesoluble polymer becomes then insoluble, which should be prevented. If the gelificationis very extensive the industrial reactors have to be stopped and cleaned.

PREVISÃO DO PONTO DE GEL

When the functionality > 2 the conversion (p) should be redefined :

o

o

2 (N N)p

N f

−−−−==== number of reacted functional groupsnumber of functional groups present

at the beginning of the reaction

EQUIMOLAR REACTION

n

2 2p

f DP f= −= −= −= −o

nN

DPN

====Since

c2

pf

====

o

o

2 (N N)p

N f

−−−−====and

Once gel formation will occur when DPn = ∞ :

CRITICAL CONVERSIONConversion at which gel formation

will occur

In the previous example of phthalic anhydride with glycerol:

c2

p 0,83 (conv 83%)2,4

= = == = == = == = =

In practice, the critical experimental conversion (~ 77%) is lower than that predicted by theCarothers equation. This difference stems from the greater contribution of fractions of

higher molecular weights

The conversion as described in the equations above is only valid for an equimolarmixture of functional groups of 2 typesmixture of functional groups of 2 types

NON-EQUIMOLAR REACTION

(((( )))){{{{ }}}}c 1/ 2

1p

r 1 f 2====

+ ρ −+ ρ −+ ρ −+ ρ −

The statistical approach to gelation (Flory) gives rise to an equation that depends on parameter r (stoichiometric imbalance), parameter f (branching monomers functionality, i.e., with f > 2) and parameter ρρρρ (fraction of functional groups of the type A that belong to the reagent with f > 2). The critical conversion is given by:

In practice, the critical conversion obtained (71%) is lower than the experimental one (~ 77%).

The prediction of the gel point is important in the control of the crosslinking of thermoset polymers, because if the process is too slow or too fast it may have undesirable implications in the final polymer properties. For example, a foam can collapse if gelation occurs very slowly or, in laminated products, a too fast crosslinking process can lead to brittle materials.

A fully polymerized thermoset can no longer flow into a mould and thus cannot be processed. Consequently, manufacturers provide a halfway polymerized polymer ‒ called "pre-polymer" (with molecular weights of 500-5000) ‒ which is still able to flow into the moulds, and polymerization and curing (period after the gel point) are completed at the time of production of the piece by the user, which adds a second component that induces the polymerization reactions and continuation of the curing component that induces the polymerization reactions and continuation of the curing process.

CLASSIFICATION OF THE THERMOSETTING POLYMERS

TYPE A – when p < pc. The polymer has not yet surpassed the critical conversion. The polymer is still soluble and fusible.

TYPE B – when p ~ pc. The polymer is still fusible but its solubility is very low. This is the type usually provided by the factory (can also be of type A).

TYPE C – when p > pc. The polymer is highly crosslinked. Insoluble and infusible.

TECHNIQUES OF POLYMERIZATION

Polymerization of vinyl monomers(chain polymerization)

• Very exothermic

• Low activation energies

Polymerization of non-vinyl monomers(essentially step-growth polymerization)

• Slightly exothermic

• High activation energies

use of high temperaturesuse of high temperatures

TECHNIQUES

• BULK

• SOLUTION

• INTERFACIAL

• PHASE TRANSFER CATALYSIS

- advantage:contaminants free

- drawback: high viscosities inhibit the removal ofcondensation products

- advantagem:low viscosity, “by-products” can beazeotropically removed

- drawback: solvent removaldispersionand emulsionare not used in practice

INTERFACIAL POLYMERIZATION

• Useful in the case of very reactivemonomers that ought to react t low temperatures,typically those containing acyl chlorides

•••• Non-stirred reaction, controlled by diffusion of the monomer to the interface

n n+NH2H2N C C

O

Cl

O

Cl

C C

O

n

O

NHNHH+

H2O / CH2Cl2- 2 HCl

commercially it has been limited to the synthesis of polycarbonates

•••• Reaction is fast at low temperatures

•••• The monomer diffusion is the limiting step

•••• Reaction at interface is faster than the diffusion to the interface,thus the initiation of new chains is not favourable higher Mns(resemblance with chain polymerization)

•••• It is not necessary to adjust the stoichiometric balance

PHASE TRANSFER CATALYSIS POLYMERIZATION

•••• AQUEOUS PHASE containing monomer

•••• ORGANIC PHASE containing monomer

•••• CATALYST ex: quaternary ammonium salt

IT INVOLVES A:

NCl

NCl

Exs:

• The catalyst transports the nucleophile monomer from the aqueous to the organic phase(where the nucleophilicity is increased by a reduction of the solvating effects)

It is also an interfacial technique

ClH2C CH2Cl +n n NC CH2 C

O

OH2O / benzene

NaOH

[PhCH2NEt3]+Cl-

CH2 CH2 C

C

C

N

O O

n

Ex:

POLYMERIZATION OF ISOCYANATES

ORGANIC REACTIONS OF ISOCYANATES USED IN THEIR POLY MERIZATION

urethane

substituted ureaR N C O + R'NH2 R NH C NH

O

R'

R N C O + H2O RNH2 + CO2

amine

POLYMERIZATION (PSEUDO-CONDENSATION)

• Reaction of di-isocyanates with diols (polyurethanes) or diamines (polyureas)

Polyurethanes

OOn

CNH NHC

OO

N N n OHHOCCO On +

NHNHn

CNH NHC

OO

N N n NH2H2NCCO On +

Polyureas

4,4-di-isocyanatophenylmethane(MDI)

ethyleneglycol

polyurethane

Ex:

POLYURETHANESare versatile polymers

• Elastomers• Plastics• Fibres• Adhesives• Paints

• To produce polyurethane FOAMS H2O has to be added in a controlled fashion(waterreacts with the isocyanate groups of macromolecules and transforms them into aminogroups; these react also with other isocyanate ends, giving rise to urea units.

• LYCRA ® (Spandex) is a fibre that results from the (co)-polymerization of an urethaneand polyethyleneglycol (PEG; with DPn ~ 40). It is a thermoplastic elastomer (it containsphysical crosslinks) owing to the fact that they contain in the same chainvery flexiblesegments, thus amorphous (PEG), and very rigid fragments, thus crystalline (urethane units).

PEG (x ~ 40)

LYCRA ® (x ~ 40)

rigid segmentelastomeric flexible segment

x ~ 40

Spandex has a complex structure, containingurethane units as well as urea units in its chains

The fact it has in its structure, simultaneously, highly polar rigid segments (crystalline)and flexible segments (amorphous), makes it a thermoplastic elastomer (TPE)

POLYMERIZATION OF SILOXANES - SILICONES

ORGANIC REACTIONS OF SILOXANES USED IN THEIR POLYME RIZATION

silanol (unstable)trialkylchlorosilanetriarylchlorosilane

DEHYDROCHLORINATION

DEHYDRATION

Si ClR

R

R

+ H2O Si OHR

R

R

+ HCl

Si OHR

R

+ H2OSi OR

R

2 Si

R

R

POLYMERIZATION (POLYCONDENSATION)

disiloxane

Oils, resins, elastomers, adhesives

poly(dialkyl siloxane)poly(diaryl siloxane)

dialkyldichlorosilanediaryldichlorosilane

Si ClCl

R

R

n + n H2O- 2n HCl

Si O

R

Rn

R R R

Although some siloxanes resins are prepared by polycondensation, this is not a satisfactory method of polymerization because it leads to cyclic products (trimers and, in particular, tetramers) that canvary between 20 to 80% of the total, depending on the reaction conditions used. A mixture of linearand cyclic products are obtained, the latter being separated by distillation to be subsequentlypolymerized by ring opening polymerization catalyzed by acidsor bases.

• The ring opening polymerization of siloxanes withacid initiation (chain polymerization) leads to

RING OPENING POLYMERIZATION

The mixtures of cyclic and linear oligomers can be used directly as silicone oils

• The ring opening polymerization of siloxanes withacid initiation (chain polymerization) leads tolinear poly(siloxane)s, the molecular weight of each can be limited by the addition of a monofunctionalgroup agent precursor, such as the hexamethyldisiloxane, which interrupts the growth of the linearpolymer via the formation of non-reactive end groups:

Si O

CH3

CH3x

nH2SO4

(CH3)3SiOSi(CH3)3

Si OO

CH3

CH3

Sixn

Si

CH3

CH3

H3C

CH3

CH3

CH3

• The ring opening polymerization of siloxanes withbasic initiation (chain polymerization) leads tolinear poly(siloxane)s, with high molecular weights, possessing elastomeric properties.

Si O

CH3

CH3x

nOR

Si O

CH3

CH3

xn

Zn

∆∆∆∆

In this reaction crosslinking can be promoted by addition of trifunctional ag ents, such as trichlorosilanes,which co-hydrolise with the hydroxyl polymer ends, or by the addition of O2 or peroxides. The ultimateapplication of this product may involve further heating with a basic catalyst in order increase the numberof crosslinks.

Elastomeric silicones can be vulcanized at room temperature ("RTV rubber" – "r oom temperaturevulcanized rubber") or can be cured with heat ("heat-cured silicone rubbers"). The first ones involvepolymers with DPn's of 200 – 1500, while the latter ones of 2500-11000. Those of higher molecularweights cannot be obtained by step-growth polymerization, and are often associated with additional polymerization with further crosslinking.

Single-component RTV silicone rubbers consist in a mixture closed in a sealed container composed bya poly(siloxane) with reactive silanol end groups, a trifunctional crosslinking agent (methyltriacetoxysilane)and a catalyst (dilauryl dibutyltin). Once this mixture is exposed to the atmospheric humidity, the crosslinking agent hydrolyzes giving rise to the corresponding trisilanol, which reacts with the activepolymer ends to establish crosslinks, thus promoting the polymer curing.

Si O2CCH3H3C

O2CCH3

O2CCH3

Si OHH3C

OH

OH

+ 3H2O

CH3COOH

Si OH

CH3

CH3

Si O

CH3

CH3

Si

CH3

O

OSiHO OH

CH3

OH

- x H2O+

POLYMERIZATION OF FORMALDEHYDE

ORGANIC REACTIONS OF FORMALDEHYDE USED IN ITS POLYM ERIZATION

hemiacetal (unstable)

acetal

••••

OH

+ C O

H

H

OH

H+

OH

CH2

OH

etc.

C OH

H

H

+

OHH

CH2OH

OH

CH2OH

- H+

OH

CH2 O

H

H- H2O

OH

CH2

OH

+ H+

H+

acetal

Schiff base

ortho or paraelectrophilic

attack

••••

••••

OH

HOH2C CH2

OH

CH2 CH2OH- H O

etc.

•••• PHENOL-FORMALDEHYDE RESINS

OH

C O

H

H

+

OH

HOH2C CH2

CH2OH

- H2O

OH

CH2OH

CH2OH

OH

HOH2C CH2OH

CH2OH

H+

pH < 3.5– para director4.5 < pH < 6– ortho director

CH2OH CH2

2

CH2OH

OH

OH

CH2OH

∆∆∆∆(>230ºC)

- H2O

Resole(low molecular weight prepolymer)

DENSE NETWORK

CH2 CH2

CH2

OH

CH2

CH2

OH

CH2

CH2

OH OH

CH2

CH2

CH2OH

H2C

H2C

Resite- Insoluble- Infusible

Reticulated polymer

Reaction with an excess of phenol

Prepolymer (n ~ 3 - 10) (Novolac)

In moulding, further addition of formaldehyde (orparaformaldehyde or hexamethylenetetramine) is made

OH

+ C O

H

H

OH OHOH

excess

pH ~ 4.5 - 6

SnR4 ou M(OR)n

- H2O

•••• PHENOL-FORMALDEHYDE RESINS (cont.)

- Boxes and parts of electrical equipment- Switches- Telephones (old ones)- Heaters, etc.- Furniture coatings

DENSE NETWORK

CH2 CH2

CH2

OH

CH2

CH2

OH

CH2

CH2

OH OH

CH2

CH2

CH2OH

H2C

H2C

Resite- Insoluble- Infusible

Reticulated polymer

OH

CH2

OHOH

CH2

n

Novolac(linear prepolymer with n ~ 3-10)

∆∆∆∆(>230ºC)

CH2O

- H2O

•••• UREA-FORMALDEHYDE RESINS

C O

H

H

+ C

O

H2N NH2∆∆∆∆

C

O

H2N NH CH2 OH +

H

O

H

C

O

NH NH CH2 OHCH2HO

C

O

NH NCH2

CH2

N

CH2CH2N

CH2 NH CH2

C NH CH2O

∆∆∆∆ ∆∆∆∆

+ H2O

H

O

H

H

O

H

+ ++

urea

C NH CH2O

- Furniture coatings- Electrical equipment

∆∆∆∆

DENSE NETWORK

etc.

CH2N N CH2 NCH2N

C

CC

C

CH2 N

CO

O O

O O

CH2N N CH2 NCH2N

C C

CH2 N

OO

Reticulated polymer

•••• MELAMINE-FORMALDEHYDE RESINS

C O

H

H

+∆∆∆∆N

N

N

H2N NH2

NH2

N

N

N

N NH

NH2C CH2

CH

HOH2C

CH2melamina

- Furniture coatings (Formica©)

CH2CH2melamina

∆∆∆∆

DENSE NETWORK

etc.

HO OH(n+1) CH CH2

O+ (n+2) CH2Cl

- (n+2) NaCl

NaOH

HCH2C

O

CH2 O O CH2 CH CH2

OH

O O CH CH2

O

CH2

n

bisphenolepichlorohydrine (excess)

prepolymer (DPn = ~ 3 – 10)

EPOXY RESINS

They react with theepoxy end groups

∆∆∆∆

DENSE NETWORKS

- Strong glues (ARALDITE© type)

- Glass fibre for leisure boats, laminated, etc.

HO C OHCH3

CH3

bis-phenol A

•••• A PREPOLYMER is made(using an excess of epichlorohydrine)

•••• The CURING process is carried out, normallyby addition of a polyfunctional amine (f ≥≥≥≥ 2)

•••• PREPOLYMER FORMATION

O OH

HO OH + NaOH H2O + HO O NaCHH2C

O

CH2 ClHO O CH2 CH CH2 Cl

O

HO O CH2 CH CH2- NaCl

O O OH

Na

NaHO O CH2 CH CH2

ONa

OH O

+ H2OO OHHO O CH2 CH CH2

CHH2C CH2 Cl

(excesso)+ NaOH

O OO O CH2 CH CH2

OH

CH2CHH2C

O

nCH2 CH

O

CH2

prepolymer (DPn = ~ 3 – 10)REACTIVE

REACTIVE

REACTIVE

•••• CURING OF AN EPOXY RESIN (with a diamine)

- The curing agent can be an amine with f > 2.

- Formation of a network (dense) via the establishment of crosslinks” in the epoxy end groups of the prepolymer

Reticulated polymer(dense network)

- M. P. Stevens, "Polymer Chemistry - An Introduction", 3rd ed., Oxford Univ. Press, 1999 (DEQ Library: 2 nd ed., 1990)

- G. Odian, “Principles of Polymerization”, 4th ed., Wiley-Interscience, N.Y., 2004

Bibliography (Non-Vinyl Polymers)

(Pedro T. Gomes’ )

- M. Michalovic, K. Anderson, L. Mathias, “The Macrogalleria”, site do Polymer Site LearningCenter (da University of Southern Mississippi) (http://www.pslc.ws/macrog/)

POLYMER SYNTHESIS – POSSIBLE ROUTES

• STEP_GROWTH POLYMERIZATION(Polycondensation)

- Applied to NON-VINYL MONOMERS

• CHAIN POLYMERIZATION (Polyaddition)

• CHEMICAL MODIFICATION OF EXISTING POLYMERS or COPOLY MERS

- Applied to VINYL MONOMERS- Applied to some POLYESTERS and POLYAMIDES obtained by Ring Opening Polymerization

A Classical Methods

1- Non-vinyl Polymers

2- Vinyl and Acetylenic Polymers

Polymer Synthesis

2- Vinyl and Acetylenic Polymers

•Radical Polymerization and Copolymerization •Cationic and Anionic Polymerization •Coordination Polymerization•Chemical Reactions in Vinyl Polymers

B Modern Methods

•Coordination Polymerization (Metallocenic and Post-Metallocenic)•Controlled/Living Polymerization

Block 2

Vinyl and Acetylenic Polymers

Pedro Teixeira Gomes

• RADICAL POLYMERIZATION AND COPOLYMERIZATION

SYNTHESIS OF VINYL POLYMERS – POSSIBLE ROUTES

• IONIC POLYMERIZATION (ANIONIC AND CATIONIC)

• COORDINATION POLYMERIZATION• COORDINATION POLYMERIZATION

• CHEMICAL REACTIONS IN VINYL POLYMERS

Block 2

Radical Polymerization

Pedro Teixeira Gomes