h q p Xiquid o r ~ @ t a h w%bB a t 2 W ipealtivr dieL.la8t~io

aM#eSrlapj have bean ayaW~1d~lod aad $hair pogsarfiee

irnsnt&a.trd5*4 athr d~~loovery o i ~wiat~*a ~slaatia

*i.f@ot bg &had6 an& ~ e ~ i r i 8 h . ~ $far* macbefllj, arr we

how dlreta&g dim(nruoe4 &a %b, pravioulr ahchspc*rs, .Oh@

a crarapueao of igtaxaotiiom belbwarn ye--% &&pala.

ail till61 8olsauLos. " Rt .~ laab~ ' i a sDu&er ak9 Sqrak*.e9ab

i n u a d w a a d i w *a Jtrrau*a oS tWmrokauJsrr txxO;ax&~-

nta of rrBaUo 4lsbrab;tio 0one.bentra

WWI a a h n up i n tib, s m o t i a r mrraer.kfo an8 JdaoQogio pharea

cf rclwal eQnroDuraZ4 ~ y e h t a d sraa.k6gcao: cregpaundrr,

Ohrr %%?w a0w8iaa ~ c r v b Z o h ~ 1 % dirssilusaed i n tihr prpreviow

atapa%r. FB. t;ran@tti~rm tmperawm a$' Sire a - a ~ s

#&died are i f @ dl@& i n table 4.1. Slmho$rAa zretlaxation

studfaa (xrp Zo 13 M a ) wmre &sag ordo on x few cPawauaBa.

[lfieleo(rcia ar$u,uliao vrra t a n yp onlg on ampounlls whiedh

wexa aararlXrilbfa i n rtMPZloira% &uant~t f@a, j %ha xloeu1Pa

we gnsanled and biecaun@e& la lXhia ohaglar.

(1) 8.katJ.o &ie;1ib@.Qpi o ooneQaEIW

tega$ic! sin& mmallko A *@*a are optSea13Jr untw&ali

mand benor possess fwo 4 1 a h o ? i x i ~ aom tantat e,, lpwalle2

$ c ~ %Ere dbaa tex iurd &ti 6% pir4rlpen8?letrXw &r"dirraotion.

Ilhe aim sad colrrwtiad Q;C did)hctxfa b t l i ~ e t r ~ ~ ) ~

(L3E Q* - eJ) & O W M UPOS tho pernama* digel. P S ~ ~ % B

1psa pols r iosbf i i t i s r Dha mleQuLre Fm W l i k e

wXcdlraur*ra, Zhr pobsleuablXdty snlrrolrspy ( ~ a r a,, I. a,)

l a a3lwaya poeaftZv@, i a tiba a % c s ~ o ai p r r m n f digabr ($rape $he aelwlobrie onlmtotralpil i 5 goaiUve Bpnd

n&aPlvaXy m Z X .

Orz fh. alrh.c hiad, a6 bfo%ccwia rsnierofrepy

o f golarr @oaprsu&l~ 8epeMa \rgm .tho #igtn of the dfpQTsr

conbribu$&orn. IO fa pooit$+e i E 4ho aat d i p o h &@mat

p of O b tr3rora6ule m b a ar rmali an&@ @I$+& the Jlw mi@

a%& f a nalsszfi'tu i t r the armgle -46 by a aruS;Pboietlp

&tEOJM l a &%rg.* &&quid *rJrotsils with b o a tw b&&ar

am3 P itla?&6 range o f V ~ ~ U D I B a&! D L hBve aya6Bea5ar*rdr

whers Aa i* $he a&sotsopp of proUxiO*b$3L~ BTQ

g a s f o o f ~ oziontcld u ~ t u ~ , 5 me mew p o h r ~ l & ~ w , # $ha awXe raoude By aha parm6l l e S i p ~ 1 e ogef~xrf w wi%

Oha law lssaXaorxlar axla, B a0 orkmis0l@nd order para-

maex, 1 the a w M r @$ saZe+ouS~t~ per rmf* vatum,

h * 3iW(2Z+l) Uls oavity iSaJSt fwbr, P 1/El - Zi ) ,

E -(4~/3)[(a84)/(23 4 1)3 $ko *em4&t;toa f f a M faator

anCl %the Boltmma oowbsrl9t. W, ge% fez We arni8ol;rspj

o f One dfeledtri@ oomOurb,

%a widely nerrySnig 8Sela2latrXo prog.thlar a t %he

namaUos san b~ urdarskob guulftat;ivclfj an a e bas i s

of thSa o$wQion* %xr r@%ah9va mm(rudar & B a two

Perm wiMie tha iXwcir*r btcpeklsC8 of tlRe e$%stian (4.5)

deaemins *he i x i g of A d , @wtl p &+ a w l a s r #tian

=199*, the Dwci Parma chid up an8 (;he @asgourd b a a st~@r~&

goa2tlrcn bilskaotr5o anitaotrwy. h x EJ =! 511'* the saaaad

Serm mnf $ h a DD@ .&a o~flltXfb~t*(i~ bo AS. BOX

hiiefh.~ ouXma of $1, A s > O ar & 0 , dependiw upan

wh8-r 0h(, dipcPlar ucsntsibuticmn &a lea@ or mws W m

%her ctionCribudion due OQ po2wrim&bl9f$y xuadaeGrcagy. Xmr

in$ercse~tdm2y, i f BknQ two $arm3 vidrhin athe $;;towar lar&@kat)t

i n syustioa (4.9) azcir* p r a a t i o a b aaml, I4 i a dlaaac %hat

hta~ratur?ea as i s f a d a ~ d feL(owpd in

atme ~ g p s ~ a m . 14

Ronr ( 4 , l ) and (4.2) w r ma oa&ocxhO@ the man

dlt~laaf~rio cronra2mP Is) In the nraeertio ph.eec

A# thQ d a s i f y ohan&e adl heas, $be o&mge in li a$

i i a r +ray amll ( 0.5%) wuafielr* (4.4) slad C4.S)

fnlglg tbaf " t w alaou3.b pxso Wic~dly aoinoid* wirsh eill

%x . &16 2 t# ~i?tmaf t o aainaide rr t r tb , cis ae.l.$ f w

~ n p o ~ a r m a o m s ~ t k ; e p p t*a-*oiLkjhs*asw~s. ' 5 0s

ofhlea: ~ I X I , a nat iosar~~s garii;ltte gwp b h +due

hala bQsn s>bamvad %n savrx;lnl srWqty poLarp as>mpa~a8@* 3 11

nke dfffer6nee can be as hi@ a &s~E.'*" RSso, i o

fwn8 60 decaceasr wi?tB Cl@rrrrae@ 41 f @ ~ e r a b w a t n suDB

s ~wutgly pol an^ omoundsr* 3*4 m ~ s r sad mtsx8r ~ o r y

iial2nr. ta aooaultb for these oblawvatioaa* Bm mis dslrr,

b ~ e k or the kheorg tar %at 1% mg1a~O1 ~LLiwt XDII&O wdex

eiialats i n nasairua.

E&lrrr*tr tklaozry of dSehkactrt'P~ aaatropy, abenrrall

&aorbtiaallg i&et t n tba mmti@ phP@e %hwZB be

Let#@ QhW a6 extrapaldated Y&W lfsWl the ikaaQ~0pi~

phPsa, me tboslediuaxl clusw 5a x@@oduo@& isr. fig.4.1.

%% poetiOiwe jwp in tha voJw d obewrmd a t %IF &dr 5ntrsrprra4 aa due to a dil~aaur4inuaarr desmarro An %ha

an$ ip .s~al le2 uwrnlP12;24g~ e*Qwern acll8iztJbawig rsr01~)aaleo.

%%e drasreaaa o f 5 wllth de#cseusc(l o f %utfliem&re is r r v i d m % ~ ausp to IWPIIBJSIO in the ~ln%~e~$1~6~ne5

orClagIw a% rower? %e%arak~crra,

( ii ) w u t r f o relaxa0iosl

2% ia w13 kstown $b(~hret dleleotrio orrmnt&n%s am

f ~ a d a e n ~ ~ . d~endanP, En the wmtle amercbfa phase,

the rraleavlrhiorr of e, aormspoMAnll: to rcsoptaabtllpn

abmt the J@Y&S aclrouPur and@, wow6 ID tho uEft m@oa

whale relaxet;lun of a,, * ndarfag Srw aaXsculsar slroxketr$er-

tiam &out Cba &%or?! acLaouEnrlr axis, otawm i s ms or am@%$=@@ erern 50 4 % ~ re&oo. Ih5e d f Sr~~f%!ta in Xlrealuanc~fr

deprsnden-e o f s ,* mlg cs, oaun tm WB l 2y uMar.n*od an

bho baels M fh6 Pact% ttiati d l lLqpi4 @rp%t&3.@ gonaaess

orri6aa;~tionrrl order an0 heaw fa* moXoeuZsr reon'i@n$la-

tion# aBouQ Oh@ short a.%2& 81 bhe sod like m@Z@rrule w i l l

be s%r@nglg hfndar~18. 2M Xlsw freqrrsnay ~@L&xabti& el!

FIGURE 4.1

Theoretical variation of the dielectric constants C:,, , (;L. , cis and 'T = ( + 2 €-L) /3 evaluated for A*/B* 0.5

(Reproduced from ref.17).

a,, vsar f i r e % obmesood by mlsier an& &5er1' i n

rerersS nelrbera of the p a s o v a i s o l e ( P A A ) m ~ i e s .

2hey cbrrro$ig s t t r i bu t e& $56 $a the e i f e o t bf $ha aombio

pot@ntiILO.

Phs dipole masent p olt a gnQl%abIl% naltina an a g l e

B w i t h t h e long molweular ax% ar hgla EOhapanenIs )sh wooladl

i n %be I@r&SttadianJ direat i tm aad y% * t r a l ~ @ in $he %ran.-

V~CIIEI , direoWon. $he reor ientn t ian o f % is hlt@ol.rd by

the aamatio wd*r r e m l t t n @ ta a low iaquaaoy relarabiaa

of c,, . Oa t h e other hand, oan reor ient ram eedLg

about the Zoag a r i a and aorresgsad?. a&Zy 6, re laxer umrRllZg

In the UEllr o r la am@ anrwr i n 10 - LOG &ti% rcPgio. 8.

$he o~ ion t a t i ona2 oxder i n %he nediuar f a %@@a thaa sna,

wt a2no crantrLhuher $a the r o k o i r ~ t l m cf I,, lending t a

a meaoad rcrlaxatlolg bt st, i n $he bX@ irequenrpraf (LO Map - ma) r e a i m .

%eir* and Saupe and Lcti@s Marain a t a 1 exleaded

%he 9Mbye2' ara861 of Qlerlec~trio r a l axa t&m i n i iqakda t o

nsamt2ora. %key d e i b e d a r a t ~ r d a b i o a f ao to s g: =

where ra l r %he o'blseW%d teLaxmtiar t im o f S,, i n the

nMal lo cagQ t0 the *&%nary Debye rehxts t ion tiaie

Sa ah% i ~Ot+op io phab*. A I A U ~ P P ~ ~ Z Q Ithat t he mbPamle bacr

anly %he lan#it i ldinal aoar@onon% &f ,Ithe diga&o rrme:rti,

they w m m abllo 60 rsksbe the r e twda t ion faalox far r,,

Xn a6 iao0ropl6 p h a e , tlba hiallzsrme %a the hs05euarttar

raolciaa%ationr is meaAnJp (lue $9 the vtnaQlsA%y eal %h%

mbiura, ?h Cbmexlature &lspandeac~ sf tha vlraawiO i s

oxpreaeed ua Q 4 * x p [ ~ i k g l C f , uhem i ~ ~ 3 *he emti'*a-

t lan anerxgy dm to vibtron?l%y s3Pfteat~ a&% in t10e f#o$ro;irta

pkiaao to& rl/l%SIE. Fmw %he Q~~fUflldea a i tPsct mtiirrdo-

hian iaa%orr we 1m18, vH * m0 snd h W e

Cale, and 0sI.e2' a w e n t r d a gmghiaal mpre-

mnbatian (no* ~13181 tihe Gale-Qo2e pZar) ukiols l a t l i ~ a t e s

the nsbuav of relaxa2tan. XO i n obtaLemd loy gZot%ing

tihe etperico*nt*& t a u e s af e e ( w ) a g d a a r tbam of tb (u).

Per the anrr .sf @id@ ralarat&on Oiw, e' and C w a r e

given b$

and %ha gelnBrs (e ' . t") &Pa m a @am&oirolie wit;& the

~era$m an % b e E' naira a& in%erseoting Wlar ati f ' * r

andl a* m am *beret o and am a r e the ileafie andl bQh

tmquenoy d;teIeatria oonstnnt.. Dar*icaOioacl f r Q m the

onniaiarcsl* plot indionfe a rltantriBut.%on 4 relaxation

%&so n . lFrrrliar abaewtatime en nema%io and aeecCio A

liiquild arye~ahxs ahat %)so C ~ ~ X O L I - C Q L ~ p lo t i s uarud~pf

a m18LoLrcske in the oaw @f a,, re l rna t ion w h i l e ii t e

ail$ 80 %n the @at#@ ail Q io$foat%n& 8 dinOsibut%oa of

relerxqtlon froqueracai*~ Ln t;P& liwtear en@. 12

( i s ) A rraheartio dia$rrru~ ai Ohr heuctw tar sham &a

4 %be heaOar 04*~1afed of aopper or* ]Raring

a seeteiwul@r I P l Q C a%@1~1 i t s kbwOB. Hicrhxom babes

wtrm m e wwn& st B o a UIilne ands (00 ) hk6 blahsat t o

av@Ld Ssrarperatario @&ie*s i n %kc aswla. Okea win-

dew8 (w) wen, pmwidect at th* sentre fa rim&

o@u1d be co$ahadl about aa 'Ow'b&ID& &xi@ gad &%ur pwition

oou24 be +wd @a a arrculeuc ocoabls) rbts&sd to $$a

boheere to ra wouxaay a f 6%. tC. 4Phfe *nabla@ uap b (u~rabr

bo$h t,, and tt ara.\rrclracsn%e oc the 5- tdwpXe by raws- t iag 'th a q h by $0'. 2M heate* i a amneed on a

PI- Betwma M e pale gaaaes (191s) of a slrong ahe t sa-

~prsrmf. %ha amxmJ: @apply ho Wo hoatr* ixs bar^ *a

a atsebilioreb aowad (ID&lxebg 169).

, ,, 4 -cyanophenyl- 3 - m e t h y l - -4- (4 --n- nlkyl !~enzoylo~y) henroutes

(nCPMBBI

/ C l i j

, d l

4 -n -~ l ky lpheny l - -3 - -me thy l --4--(4-cyanohenzoyloxy) benzoules

i n PMCBB)

, ,, 1,-I>-alkylphenyl ---3 - melhyl -I+-(6-nttrohenzoyloxy) benzoales

i n PMNBB 1

I I,

4 -n -alkylphrnyl - 53- melhoxy - 4 - ( 4 - bromobenzoyloxy) benzoates

I nPMeOBrBR1

/ 9CH.3 , ,,

4 --n --alkylphenyl-3.- rnethoxy 4 - ( 4 - cyoiiobenzoyloxy) benzoates InPMeoCBB)

B I O W 4.2: Stru~tural formuUe and roronyms o f various oompoundltr usad in our studies,

(it&) B&elacrtria QoJ1 --.---- Be dkai.laotrLo oia&itaf s wore de.esrerrlna4 bp

aeaeuring %he aswaitsurae csf o p a r k l l a l gLats capaai tor

wlttraut nnd w i t h tkr mapXe. Pho ~O11watLa d l wP%m QX

Oh@ BZ~ttl@~fr.%a o@Tb used i n dhavn in fig.4.3be %ha c r l l

Quiaais$Qd of two t i n axida absltej platerr (0) whiQh

ohiah enru~o c$ood eksetri <sd contreat. TYI* orre 1, w w h@ld

rL#id'L$ in a aoppar fmae (t) ueing tacrawa Bl and " 2as &ma in f'ig.4.fb. Tho fmw aorrXd be ia~clxtad inta tho

harntnr atrob the% (;he acr3.1 was poeitttm~d at thn asntrs

Schematic diagram of (a) Heater (b) Bielectr ic ae l l .

C - Circular par t s w a r which the heater is wound

W - Window f o r the vfsual observation of the sample.

N S - Pole pieces of a permanent magnet

S - Circular soale M - Mylar spacers

P - Platinum f o i l LC - Liquid Crystal

G - Glass p la tes F - Metal frame

S, & S2 - Sarews used f o r holding the g lass p la tes i n posltion

L - Lead wires (shielded)

T - Copper-Constmton thermocouple

N - Nozzle.

rwmr uy aald tm@a4 mdr then t;bcsrou@Lj waked YSW

The aeU, w e fil led rim %he wapl* vhfb X t

warr in the mmtlo phaua. 'Phe eraU u ~ u than iaparQld

in%@ $he hreantu asrrembly wBl& trauar w~ouatod slhd tam f12XeQ w i l t h nitregoft. aam worr t&@n t;o @muroe $ha%

aha39 wbre 110 a bubbk* In t~re r ~ m ~ p ~ .

i aaargn0tiQa i t c s l d o f s&~wM 2 14 P#aiawra @as

uasd tor the amp26 eaXi@samn%. Far aaarwrrt~trnf 6f

E,, r *be RWZB war all@& ~t@epal@iaaZly 641);CJ me

s h c $ ~ i o fi;~iel~ wata apg~iea azoay& C B ~ .caArearar (3' rr il' >, k, waa aesrtruxed by srlimlw %he aeurlp'Le hmga?neourf;tr

mb applyfw bhr eSecrlieiQ ;Clad& gerr;lrePdiatcler $0 a% direafkox! ( 3 J 3 labsame of &a ai.@otia

XSeld bbr darae%n vralres frbroa poSn% to @@Axit a& 'k&e

waaaum8 d3.elsotirio oanrew* h.s 81 va;Luo br$w(ran irh. Ow

pinoiwX &iarScr$xi~~ ~6rnrsnO;s. A# f b aawatSs f ie ld

ir inoxwraw3, fM sraz~ssusweQ t&wau of r ,, awl a, aha-

unM2 'aaturafion* +alms are rsaarhed whaa Oh, m2eakatSon

i a d E e ] i r r ~ Mrorrgihouh 'Ikh~ e8~~1pZe. %%A# aratwatiaa $$st

uar nurQe i n a22 sup *r9be;ur?*arxlPm* A fieXlti rrblrsmgth o f

&J4 Phuaaa orow fot~und t& yield nsa-&Men s a h e s i a alS

hhs aanpaurxffr skdi04.

21'1~s 3rsw fc@$uexl@y blahidrchslo ocmtunJ;s wart)

nouaciure;d by w f r ~ a idwne Xexe LLbrMge, mPlOd@Z 8642, BI

u irretd;lu.encg QS 1592 Ha. T?w aag,~?saa&.tZmea YWQ =a@-6

%D ea raaawasr beCfer S1.0,g md heme f?a@ cmld be

Ibam as aaauraoy l a %he se2mntlee =&&$%a 0% k, ,

&5~rfiusmbn%# a 5 p f ~ i j r r l QialAlatrAo aam

t~Orsn$zrdiar usxe mde in fha iroO;xapio, nsProtia onb rmolrio A

pkao*r. alt

bp arlwlf oooalng bhe arim$L@ # m m We aaaaia *a a% erras@%&@ s pharsa in ill%@ pmaernoe o f @be laergnorfio ifaf(l.

(ri) DieloeWo rolatation r tudioa - "m. exprrimn$lal @a$ uS, ware th *am *&t

uaed im eOQBia araaurrr$a$r. Xcrwm&r, me %An ox&Qa

wan UP&,

Ir)rr Qtqterrien weta aaar~rrraQ up iro 13 PIII5 am&*

Hew2886 Bacsbr4 LO irg*daaga* runwJxs@s (FJcrb.1 4PBPI).

We sewbar& aa@*Ctitruraaa and oo&uo%ames wsrs aormahrrd

for Xe&d Zaduot~noe. Bob: @a~ll. crapruttnd, %he reart anit3

isuzh;ln8u:g erlcnr e r f b@"UI e,, and 9, wms msa@us& a8

oarlow to\nrg@ra-twgasa. The tem$aratwa was r%hblllisad

&ti f tolil dre;lne& v~Lu8 f c a a6 X bwZ h!%W-Ui-nbltx befor h

takAw Icll9ssur~1li@nCrf. T'n arIPerc Zo @beak WT g x p w i m n ~ l

I;@% Up fPI1" d l ~ p 8 i ~ b S ~ f t ~~(~dll~i~mma%@. W b Q ~ S I P ~ Q ~ O U ~ bt11diiE44

cm n-hry~y~oj~o'BtS~?Usny~ (7m). &ku? lrrlsparirsrcsntal raauLt~ were Sa wetasaanc: wlth %be ca~XSemr awki&kP,la in %he

c ,, t"ealurno8 Sn %r, ars;weuW ixe%uasw ~ m g a for

all fha c6pIpoundr shl i isd vrhile o brmd slatanation 6 f

s4 war abat*lt.ved i n Oh* a m p a & *Wr%y&phagyL*f 9-

~rethcx$-4*-~4~-~~mbsaa~j10~;1~b(1~~;0eO~ ( 1 Y ~ & e m B ) *

( A I iE..t&~ &tsz_Bz2gAu-cn~P.n& 2Pm $t2imlm% diellraatrfo erprtsenn%a s ,, en& &ti ,

averwe ralw CI ioats~rgio vaillue at, apdt *Re

dtr~2ec.tsla anlcsotropj (A&) ahwn tn figwe 4.4

ios: 12 BBWB. ?&a srallcaa;t; Xeotiuraa~, ore (a) st, inar?c~@@ear

w i t k the dearadictg o f b*nngJ6S&WZ6 i n trh@ rrrmtia phOw

bul @ t & ~ t s daarsrasiw fair ly r~jr l%ly a@ tM teap@r@&ire

itil lowsurad i n t h e meaLia A gharre. me raGe of deeselasls

&oe@ cllr~wm at lowar teq~o~sat~xaa; (b) e* h s r ~ emertly

Ghar q p o # f tlr tr@nb t5)rougk %he eta?~.t;e, @f varhP ;t tf on f ~a

@omwhat rawla SAM %hati 02 &,, I ( a ) &her two crwvear

arom at - E " 40% rare B h t A t ahsvngcaei ialgn f i m n

p ~ s s l t i v s t o w@%,tfwe at that O@mwrrzkhrrca; 8) T Aneramae as

the %n~er@tu.ura is X C I W B S ~ ~ in the i@oGroglo pbaar slnd

&errrearpaat. i n tb suss0pheneara. 'Patie vasllatioa af 'ii: appaart*

%c aksw ti rrusy at Tgf tb an~1~ti~)tio~iaotropio Wamlltf o ? ~

tamparatuse.

'&gee t;afsrse$in& r6vsull;rc ban ba undwtrrstosd as

Jolloors. We bavcr, &ova W e s i rn f iea~r l , dlpeSs wmntcP

of vglri e)tm bwd s ( Q ~ ~ o x I rrm H B I ~ . 26) of an I P & M ~ B mola~ubm

i n f ig. 4,9. 'lha e ~ a f Oion all %ha mol@ou;Z@ t a t not

k a ~ w n but the three gheawl r&w@ me v s ~ y :~&f&Ly ta

TNI-T

FI0.4.4~ Temperature variations of the low frequency d ie lec tr ic constants (upper part) and the d ie lec tr ic anisotropy (lower part) of 12 PMCBB measured a.t 1592 Hz. TNI - T i s the re lat ive temperature, TNI being the nematic-isotropic transition tempe- rature. The arrow mark indic;ltao Cha nematic-smectic A transition point (Tm 1.

The most imporlank dipole moments o f different groups o f an n-PML73B molecule (taken from referenoe 26)

Becoaag pasktireb aof h &&her Bepujwrature5. n u s WBIP

and &iem*cmr f%@org gWfete $he Peverccsl QE A c in the

iff ghese &lab kaaa beern tndeatl absto.od i n 8- syefaasm. 14

2kL.r m@e!ta;lnl$~~ Q O U ~ Q be a ~ n t S l b ~ f P w to Chs

rsveaarwtal o f ?&r sfan iaf at i n l a PWgtfa aha, but we

mot not@ raatw ar'l8ittoarat gaAnt~pt U f t i a the ealy

meheisa, Z ~ i h a u ~ d h t e deerbbp~4cad with A ~ Q X ~ ~ X I . ~ iaf

I ~ ~ W ~ X ~ ~ U P O (PI- ew.d.~).Z W C U I S ~ Z ~ ~ WI@&l i n the

oppokftoi liinnnss, wfi i~b ootDT4 be orti bribu0srb t o m ulwma-

tka d i p o l e ctrrm1ation fsoborns f a r and OJ* w&%Z bta

l~mltn anla OQ Jawat e,, and a m a s ~ 3 ~ .

pcagosed t t n ahuapte~ 1 x 1 to uad~rstana the %herrral

rrPrPation ~ p f bllayer ogaraiqe i n nPMW rawnd stbr

em la^ e088paud6, The t~adel WET&- %he infex&f&a

tal ion fn %he bilayeyaf l o l shmm i n fi(y;.rl.Q. En

QelrpauaAla an cnwrlap of f"t axoorarruo awe6 (4.6b)

uoulld xesult l a skong *capu&lve iatrr@e%l#m between

the dipole mamnt 6f the aywrto $;ccrup of om m@&(~cule

and that of on% o f %he %&Car greuplx of Lhs oth~i?. W

digclnar? a @jrt~iBuZSLon t tp Wbhaa int~ilTaatt on csraxl&g weu18

bs andsurar @ban err@ @ocrlug, ocouxred onZy mar the

agtenno en8 e;roups &a & b o a Pa fig. 4 .6~ . S w , caa %he

f ernwrafure is lowsm4, aorg and mrl~ nwbgr 45 ~ 1 . 9 -

~ t i I g @ darer anDd~~znlTrt1 e r r : ? ~ o L % n a@ chaw&% bn fig.

4.6@ (fey ia $et :~52sb iltaaual~isa raw ubiap%ttbr f X X ) . Th28

laadrr Go mn %numemous srgamfon l l r f We layer e ;aa iag

wit1.1 %he ( 4 o w ~ ~ i w of t ~ & r ) ~ r a h ~ e . '&ia aeabni&@

auacPun&n for %!a@ i ~ ; f r r l e ~ t r l o yraper%A:lecl as' 32 P m B

&riac 80 %owe2 temgesokrc~s, a hrga mu;~~&psr w f x~oleaulaa

are r@wuiattr& i n pai ro war *~aer cpne , ~ g r ~ % p a d %ec

crantrtbut2ar of tlha dipole so~lrarnti o f tha, ayeno end grsug

to the g @ l a l ~ . i & l l S % ~ ts i i t@~% r i fac t fvo ly m d ~ ~ ~ ~ d e

@va@ rime tio E\ taretgx rndudrt$~% o f e,, ~QPI Okre %@we-

FIG , l t . 6 : Sckic'rria.ti.c tiiag~axiis showing .the disposi.t:ion of

v a r i o u s d i p o l a r groups of a p a i r of ( a ) n-CPf.mB,

( b ) n-PI~ICUR niol.c:cul.i?s w i t h an ovcu.l.ap of 'ihe ~1Y01113ti.~

c o r e s , and ( c ) a pair. of n-PI.~CL~B rnolcci~].(?s wi.l:h an over.l.np of the polrrr cncl groups.

rartwe. %ewe tr~ndlas i r n ~ , , a & sA . J P ~ E ~ ~ W lead

20 thac severwe1 af as.

we merlircs er Ewbher mark rts&aqnrd$r& ti%@ iarrmam a$' e, with 8hrorera8e 5f Csw~rntum. Aa 'YIO w 3 3 1 gee

lstsr, the t.eXaxstictn sf in the @care o f r@bt& aom,pound 11 PB&mB india~rrrals~ t.bt th+ ;pair& aeeoabOeQ - amr tb aoyaaia groups rserZenO as a ariw2a. Wf W w

f Fze wtiaa aP the (a~%er~tal 10 11(636 3886i21@ p81qmaf olritw

tia the Jwg t a x a ~ . ff $he dlfpola.sll: gxoups aon6ribut9rrll;

t c wt af tlii6) t w o raelfwaulatca Sra %hr 130~ix eta ~&voowz&~~(

er22snts4, tlsia yokrPaer%l~n o f tllr mrdtua j2e~p'ptmridSaulcfr

f a OhO Yaw axis ear\ inurnam Q#& %o the pair f i~cgm6i l ; l sa .

Xn t h i e awe, a@ IcW teaMS*oCure &I lowexed, hht. n w b r

o f sue& psire Smmmcbt-r 'leadla& ts an Amweacre a s i ss . B e rewrrmJ 05 Oh@ tars;r6)2'12&~@ mr5aU0m @I: k9m e,.,

e z l l d el in & 1phsrae a~awrbd $B &!&a&@ Sar %ha 8 pbre

shws ttw iqartwt 3611~2100 111 Zaycsrlng; m9 C?-r@

mri%,dW@a 0s i t n %f;Puob~;rrr@ ~ t p C k i 4drelao"tka p o ~ ~ c s ~ % t @ s r

o f thgr~se awpeut~38.

%he di@XacaQr2 8 prapaaraa?m o f 10 PYlIsOOTtB and

S 1 PPle0UBB &re ahmn i n f&@.4,7 md 4.8 scs@p%ca%iVePg.

Xn bath o w o d w , r ,, taomztaaiee ~ n w tbr Zemgernture

B t l btaareta8(PB1 flron %x. It athI)rl~~~ axaa%Xlaum,w~oln ira

6

6 .O

e: 5.5.-

5.0-

1~ - ;.7% --.--

77-- &

$2

--R-O--..-_o__b

€is ----

4.0 ~~~ - -

1.6 l - L - . _ L _ _ , ,

72 48 2 4 0

TNI-T

FIQ.4.73 Temperature variat ions of the low frequency d i e l e c t r i c constants (upper part) and anisotropy ((lv~er par t ) of 10 PMeOCBB measured a t 1592 Hz. The arrow mark indicates TAN.

FIGURE 4.8

Temperature var ia t ions of the low frequency d i e l e c t r i c constants of 11 PMeOCBB measured a t 1592 Hz. The arrow mark indicates TAN.

a1ightl;l brordw as tD Pmm, o few demo06 orbme

"Jim *nd f k n saat$*aubly (Iw~eoriw i n OIte A phasa.

Thir @cans Ulerb amecaUe i t ke f#Wt a a r d a ef"teods

am8 fell8 o few de&maa *;bore am, @lm6 tho, Q~a~reaspOa-

ding &&rat of t i t i o n i a quite om11 i n both tho

sarrpmndr (roe tMbZe4.d. !&* 4enzloaaie of r,, i n

I$ i r muoh

Zhlr l a bur %@ %he, wsh US~QE rw&&@ of $es(p.m%un o#x

nihteb 8 ha i phoissu la iaOlbb10 I n 1 1 PWm1113. to 10 FNoOOPfB,

ars bollperrture $6 2lsr~gu*md e, starts Snorm.lxrg( a t or

relrrt&r@&$ M(&h bmmrnr0lrr~ Sn $ha 19 pk~oca, rPDd @haw#

a realalE. ouop Ub peak at Pa. Pkir m y br o w a d by

tbo alstalimnb &we $0 Ps whlah ka oXsa obsa?.tsd i n ootna other aqgpowds b W t IBWUJF a ham&(ttrr~pio dim- mtz' olw. t o gU. Xn $1 PH&Q8b, a,, dmx@&@u ldth

droreare o f teargaraubwe i n 15.W ld pbnss, ot*im a bmad

Painima @lose 00 %I U D ~ bhm ucron8inaowJy 5rmxsases $n

Ohe A phwr with I~WBS~W ~t *aper(~We. Be QIX* l$b

p e a l a abnwrs8 Sn Wiia aaae inb2celim a tietau? ~aligta-

laan%. xn bo* t tm oaceor~r, Z rh~wa er peraftlive j u r r j ~ at %x anti drorww r l ightfr as $he $eElp.rcnrtur'(r $8 %no2w@sd

b the isotropio phew. % sbovlr~ a atlightr inax@alnpl

bm& i n Dha ten* rsambr wkSle i t m~ntna gxiaetio~irlLy

canslant in wr caXersntla haas3owe wSf& deorawe 05

fem@aarrrtws i n %ha LI-@&it!i agy@WXXlne ghww. s,, e4

.&L& haw auerpaat hlglhw mXws 1" nPl?gsO- thaa in

the oasa of 12 PWmB bQ~w~te of the a r d b l d % m myaen

atior *%ale& fuPo o high po2PrrAaPrbili.ty.

i%o db@Laolarle ooraaxRts of 9 P W B , 1u PWli)B Pnd

12 P-B (nitro raaolgwart o f crorpsrutde} are abown

&a f21&rff.4.$-4.1I. ma* a&+be%r&e properUao 9 PMiBB

($&&$4,9) u e bxeo9dly arinflar to $hms of 10 PW~OCD~]~

(fig.4.7). gaF %he texalparawro tar Zawwed, c, r t W s

mrewipl~i: &kg f&n"ly b&h tapsraDuro S w @bare %a.

a , , &tart# dee~eaal~yg Y C B Plat 10wr twp~l~p1.lbtr~a.

Laiough @ti11 & m e 'Pm. %he de@1?0me ~i el , ~ O O O P I Q ~ O vex+y

lcyn~&a t%f TM* %b@&. tredrs E Q ~ L P I C ~ A O ~ 0f

(a) @hart rrarrgs D ~ & ~ B P aU@dlaoQo near u~ i$*ntlane9x

awllarr (efiapter f ) -%$&a A Xike rrhort e oHar & Q W @ ~ D ~ E $ S in the B pXnaaro 1~sadCLlng *o better m%ip;u~~&leI.

s o l ~ a . ~ o h s srsrwiotiana, araal @OM efia@C.ivb 0 m a ~ X l o t f ~ 1

sf f a n g i * u a d Q O I B ; O ~ ~ U U I P ~ ~ ~ S ~f ZF~O a i p ~ r O awn$@, and

f b ) M e atraw raLrir*t.iat? o f LeaipX. fieLd wiEh L I ~ ~ S ~ B L ~ W O

whPeh ddi#eM@ 0 8 t& ubrs%rUve nwsbar a t aasrtmte.tred laoh-

cprlo~ and ,+la@et aD&lruTaa. Xn Entha @we af 18 P m B

( f i g , 4.10), a,, erh&btbitii# a 03@ax4 wigar%ive $q w k f b at

~haha~e o laaha h~rcor~Purranj; iaorrea*a aa tiM ample is caobd

aom8e !Em. *&s rats@ af d*esgdpruo a t a,, aa& iaucrseae~r o f

c, saa tkLB t~~wemklze %a 20*re~e(Z ;in dh6 A @ h a * w e @mwhat

FI0.4.9: Temparntwre variations of the low frequency dle'lectric constants (upper section) an4 anZnotropy (l.mer section? of 9 Pt%BB menmrred at I592 Hz. The arraw mark indicates TAN..

FIG .4. lOt Tecipernt;ure variations o f the low STrecluenoy dielectric cnfisLanLs (upper part) and anisotropy (lower past) of 10 RltdSB measurn8 a t I992 HZ. The arrow mark indicates TAN.

FIGURE 4.11

Temperature variations of the low frequency d ie lec tr ic constants (upper part) and anisotropy (lower part) of 12 PMNBB measured a t 1592 Hz. The arrow mark indicates TAM.

sis%frar. Art daawaru aontlntlously Ln Cha I phw uad

ohtnngea aim beaaaw wga%ive a t %A- T "c WO@. F &OM

o gtsnrral imreora w i t h ! deorc~asrt? oZ tea@xat.tu%e s"e!%iXs

aotua3ly 5 draxolared with drt~reoara o f tCm@e#aWe i s

o y m o a q o u n d (12 P a l r Xig.4.4). lPRlsl xelgul.8 mast

probarhly mema $hati htr* c~mu45XaQion of Clrrb laagiDu61inaX

cPomgarremCill o f the #Q2 dlp@Lr memmte oZ hue, ~rsaucpfahdl

mobcduka, (iilg,4,6@) i s , Mflr ss aItiecWve ae An tbe a w e

af eymo owsuPde beo;lmrae *a LruOarm%larar Bet;ween the

Latrersal aenrgcaasnta o f thr dipo3e maunts eiT tb BU boa;r4r

woufd be regu%#ive oa $I& & * e w e ark4 waul4 aontrlibulc

*o 8 redwkton An the ~ttrtnraX1ve inQeraotauaar ZIstmrdlr tBa

In @'he DOL LO oP: 12 P m B (ti&+4.lJ), &,, i l lg .eea~@

&OOSQWX))B@ ~ i h a Q Q C Z O Q P ~ a3$ t@m6PEL*W"@ &Yk '@I%

gMa% m a tholl r,, decsopnea rl inarewe@ a@ %kt;l~(~

teqera$wcu 5s ~owwsd i l w the A yhrrsra, %r aM8rarraa a i pssDrm@ltlom2 eS1"e~lS above iCI due $0 Oh0 r(Pr~tZve1y

s%zong PirPie wB@c tz*uoz@P%fon Jn t M s compouPld. %ie, re%# of waurhtJisnts beoom ~ D O D S ~ ~ ~ W ~ O I Q ~ ~ f i r ~ w e r 8% ?fax - rP S', W3*c rF; prRPoh toegrera%mo AS i%usl f ' okmgrss aim. A t a W l S

laustr tampe~ahrers, &ha $at@@ uP vw9ar.t-%a& Seosa! Mi.

FIGURE 4.1 2

Temperature variations of the low frequency dte lectr ic oonstants of 11 CPMeOBB ~rieasured a t 1592 Hz. The arrow mark indicates TAN.

Prorm 4&

Temperature variations of the low frequency d ie lec tr ic constants of 12 CPMeOBB measured a t 'J592 Hz. The arrow mark indica'tes TAN.

Ss again dua Oo tha rr8ulol;ion ctf n w e x 01 auPtiipa~rahl

pairs 88 the tarap@ro$ura i r a inarmselit i n Ohs i;leoWopic

pImee. e,, B@QP.&D(BB a8 bhe Oenpera$ur?.e i s toware& i n

t 3p ) ) A. pMee, AB we bva alseadiy dirauaeed, pair Posrssrtiaa

%a rmora effeatliwe a% lower ~ Q ~ ~ D I ~ B ~ c o @ * end %hi& L ~ O A L I

t o rn afSIPoblve Sowarrlna of' Ohe d f p o l e nr~wlnt along ths

long axla a t %he m~2aauJlee at& hama bo ths ob@alz+.d

re%ucllion i n ct ,, .

Temperature variatiana of ,the Low frequency dielectric corrs t ; m t s of I ? WeClarBB nleesurcd at $592 Hz. The arrovr mrk Fndicatoa TAN.

Ihe dielw%r&e &@mraioa waa me1~101md tap 20

13 ms. Xn bi~t.C.t?i, we ban g1QOh.d the aieleatsia

%or8 (rg) .P a %wt !S~s o i fze$uanoy fox 1 J QJ?#W&B aQ

d%ffrsr*nb Qs~peraOucl~. 0 ,, rdLsPxrr a t a fm~~uarrey of

r',W W p at eho Lp.oweo$ .h@qprrPrgtxe oP w r p a ~ m e a t tn *ha

A gbmo (+80*1)), Oha isegusnay ahi fb lw Po hPghUrr Talrer,

at hfghr talqpsraNbucera, Tku rsrlalrertlen freqwraisla a t

velrlaua % a q r z a t u ~ e s ascr 3 @ 0 S t e n im +able 4.2. Om

65 %tias ourlours Q~ends notied f a r Pha oe*yound f8 %at

CM paah o f e:: hvrfa praatclarrlly tiba sewb ravel ~vrB d 1

trekrsal;uraa. Om would ggt.m&&t *xprru$ rr p r w e s ~ i v e

reduotian i n %his l ~ t a l ae the Sanapa,rlli,hul*e l a txKlraia~3ed

sanrs the a r i s n t a ~ t i ~ n polasia;at50n whjlah 8rtemirua &c

haighC & t h i s peak i a ~eduwd a t hima: WperoMrecr

Awe tie th degrvsae of Prh@ .s;ctea*atloaar& axslor grrrswotcprr.

As waai dlncucl3sad i n ohaptax XIZ, tfxa a0tra@tivcr ilrtas-

natf ma, Wfwintn ahr aei&bowia(g 11 OBMWQBB wrleeuLe..e

am v g ~ y weak 8ue t;o Ohe pJ?menae e i fhe bulk$ 3ateral.

@@*my Pruba$PBulen9 w& bwr Oh5 bilarmr sfmoQmxr wftlr

an ovaszLsrp w f .the a~4113CIo ~ e r r ( 9 CBLIQ Sn il;ltg./.Ba) Jrr oZ@o

is?wr~~ila me% the maclhouTcsa tend tc tJr*alr(~w@y muok o

@Wuatur(r &ti bighsx tara@scrr"atur.e. IlEhla, meme Watt t h s

aIfw*cl%A*s l a t g ~ l e BDOI~DBA~ per 1(102ea~13* a s , 4 t h

FIGURE 4.1 5 I \

Frequency dependence of s,, (dieLectric loss ) a t various temperatures i n the smectic A phase of I 1 CPMeOBB. The numbers against the symbols indicate the Cemperatures i n OC.

Za@~ea6ln$ hsrperolr~e as4 U w M a ~ r i e n t a t i o n a l polarira-

%ion doas not ham Sh6 ncvnra3. Beox*aringl $rand. Xndaeb

th lb aola-00x6 pZot whit& I6 o ae&oi rck (fig.4.16) 34

praobiaaZly iUrnt lar l a* aX3, teaperafurea i a fbe A p3Yle.

rtrr same trend is obeerve6 f n 12 QPhQl3B r l e o (figar,4,17

and 4*1@). nYe 8:: peak i n tWrs cure irr 1.8 oompwsb t o

4.9 of 11 ONWBB W tha 6 f f e o f l ~ 6 dipole ma=& per w a i t

roLuxe i a %awes f o r We highsr hoiplolwne. A# i n the nay

studlee (ahsrpfer XI$), t h e eSlsot Qf the brealring up of

the b i lager rtwotmre (sow a6 i n flg.4*60) i e enan m e

apeoBa6ular i n bhs orsar of 1t PRi@QSB. "Eha ~ $ 1 paak

a o t m l l y &@?eaaq& 9nzh l ~ r e a s e a t tcamparrrturb fxcr

~1.116 a t t30a0 t o ~ t . 5 6 rt 114'0 i n tihe A pham ( f i g .

4 . 1 . On the o % b x ha&, l a the FI pharre, %hers i r r a

rllght rrduotion i n tho gat& mlua of t:: wiW inaxeaae

o i tsmpaPatutle (fig.4.20). A. mr hat. di6auamd e m l l a ~

i n e h p t e r IIX, hh. biUyur a$rua%we t n @l@ a w e 18

twz f x a a k aad thrse the number a t Srse acleoul.lr, i s

la rger wi-f;h ri otlz~eaposdfaa~ 6nt;icnaaelslsnt of t he e i f m t f r e

dipole eaarent iab bighar tewsrafurea. A r ir t o be ergsatrd,

the @:f peak i s much rmrolliur than Sn 11 WH&BB *law the

effeataive long mmpoaenrt a$ the pr~ztian6n8 dipoXe

somen* 1 4 mush cantlllrsr i n Tihe oaae f& 11 P)[.Om (see

fig.4.Q). Gols-Uoh plot (11&,4.21) brllngr

FIGURE 4.1 6

Cole-Cole plot for &,,relaxation in the case of 11 CPMeOBB. The numbers against the symbols indlcate the temperatures in OC.

ii L ..-l - - 1 . -1 J L U ~ . L-I-I.I..I-LL.I.I__. . 1 . LJ..L~~~.,..,J... . 100 K 1000 l i 10,000 K

J Frequency I Hz)

Frequency dependencre of d,: at; various ternparatwos (indle&eld against the different symbols) In the srnectic A phase of 12 GPMeQBB.

Cole-Cole plots lor 6,,ral.axet%on en the case of 12 CPMeOIlB at two different temperaturee ('c).

11 PMeoCRH

0 114 X ion

10000K i:reqrrency l Hz)

Fsar~uetncy der~mndencra a f d;, a& va1.2ma ~ Q ~ ~ z P T ~ P L S ~ ~ U T B ~ ~

(ehown appinnt dHft.azlent; syl3iBole) in the m o e t i c A

phase oS 17 1?MoOCi3f,.

Frequency I Hz1

Frequency dependence of dl: aC various temperatures (indicated against different symbols) i n the nematic phase (N) of 11 PMeOCBB.

Cole-Cole plot for E,, f?@b%al;Z~n in the cans r r t

11 PfidmD a t two d5 f f eren t %crhpcretwes ( 'c) .

out trhr fa@$ OhaO there axe aadtti91).~)3 rct21axa0tona a t

M a o r hrepu*naier for tlrfsr tatmpouaQ, udllke i n trh. cram

of 11 QgPt.OH)%, ic g~obab lp aaulrgd by fPIe a~eTPrxabL6n

of the xsoxlsnt~t ionrl , mottos of yq, tacr obaponmt of 4~bo

dipole rolailat grrgon8iouZar $0 'We 1 orig ah. me .aua$iim

tols Chs overs l l &%pols mawnt sileryq the dLreotarr w M o h

as laes bw h a the i rpr r feeh wder i n %he mamabm (xepmeenPed

sohear~tlaaXly la iiilg.4.22) L 3 v m b P 9

wMre an4 (rt axe t)r* dip010 nountre ar loa anCl perprsdi-

oa lar t o tho r o l e a l e and S (*@oos2 8 - 1)/%> ) 18 tho

orlentat ional wder parmeter. A #Wlar ryurrtlon a m be

m i t t e n f o r the overall, dipole mo*ent perpmdloular t o the

d l r e c t o r

!i?b influenee of La no* o c d M wan la tho *+ s@lorfb-

t ion, since Cho xeox&o&artfonal moQSon of yk i a r a m<rh

rlewec prccsars Chm bath the l&bxiatimsl mohkon (about %ha

Qtrea tor) o i the ma2eou26e an$ hha rae~r lantot isn o t @* abouti

tbs l o w axle. O f 11 PXIOW Ohwe Vefy broad ~eF(a-

xoalon (f$i~g.4.23 ma 4.21)) w i t h a brood lluuJamur d 6 mt. %la rrpprrrr~ t o be a gar t iaular ly low fregwmar Ear the

FIGURE 4,22

Sohematic representation of dipole components i n an aligned nematic. (~eproduced from ref . 29).

Frequency (Hz)

FXGURE b.23 -. I1

Frequency dependence of GL in thb) daae o f 11 FavleoCnB.

FIGURE 4.24

Cole-Cole plot for GL relaxation in the case of

I 1 PMeOCBB.

xerPua8fon of p, .nd i n oorr0;rzut wa a id sot sac m$

lndioaffoa of cJ rcrlmatian i n 11 WIrrOFJ8 l n bh5* fxru~rmoJ

mn&e. C%kvloui~JJ $he a Wu~tuixe ohPrsatdri%d by thlr

blXayeo apaalnk: i ~ u rerrponrlbls bar Ohfs re1Pusbfon.

Xf the noleaulaa wkioh lava orn meehp@lryp region

only a*&r $he aymo end pwps r a ~ s i e a t r e 8 b

v* arwld expatat o lwbxil~g of tlllr caWo$don fzlb~u6nt~q.

f o r tihe r~mmt of lnyrrbh o f Bca p a l s ceor loMiw tibabau*

an mi@ w b i a h i s t sagan t ia l t o bha aprfaae 41C aentaot OS

Ohl l ~ W ( P moXeQWle@ ita web lU,&ert* O h m fhat for a aito$le

apohoulc rrarlicafiw about liSa isw axia. ?hw-Pder, the

palr would hate m9h a~eater pmWbfllW of arol.fi&l~@

aminrt nei&Bouriagb, pairls 6x inslid&& molreul*r in the

ruor i sa ta t ios poaa ra a d heme tho effeablvo frto%Loa

aosrliioisnt weal& a%*@ be large. %us PM relPuaUon wowen

t a a t Mghar

ilseqwneies cm be expeaOed Oo rBrtPr ancnoltdleo reAerrrfb(Piot3 o f

due tr~ Bh* rrcrorltxaOrxtion of Ybe fMLdduoL nol%eulee

about %hair low arw. S?he pp n h % m % C X ~ of paslrs .rm I* a d o

rafleoO68 i n b e &l@gerka oxx e i a,, u we aaw l a flg.4ral.

Fhs OaZe-Oole p lo t aor raop&lq ba e, (f@*4*24) a h @

@how# tha$ tho dieper@Son l a ohsrihatsrlsrd by a xather

br?aa4 dirstrtblrtlon o t xel~uratfon Clmo. X 'broad &tats&-

bubion i n Adlaad rxpaatdl far tihe e, ralsua'bioa a# $he

Iib.'brrrtion o f thr aolsauXst? srbw* fhd shor t arb

oantributse $0 $hi@ relaxation pzooars. %m a#lOaulss~

w4;~b.r an& hame Qbc SeosxX PlePd l e not well barfin~dl i n

this dixwbioli. 'EM la~crfer hakg.gha; for rsaorfentrttion

3a 80 ega&Z ?ha4 onXg a 82autr;tbuQioa ( o f rr~Z~~nxatlon t i m ~

@an be exgoa$r~. " ~urtbtrr, fn the oesq of I t P W ~ B

$2r*xe a re aars tiha om slye@lcnrs. ( p p k a uhL& a.rrevhp

m t the en& &~QU;EL@ QnlarI lkwr wAth ~vas&ap m f We snbire

o s ~ ~ a r t i a ~ o r r a& dOdiv&*ld~al mo1eauXae) ubioh amal6 srPrtao

eontribute $a the cxWam2p Woad dtai$xibu@ion c f tarlara-

ti9 Qn Q i m ~ @sen &in fil~.4*2rCe

n"8 a b d l aow rashm %O er fitobar illeowrsfen on

$he dl *@s@SO~P a f e,, Xlk i a r i n t e se~$ la& rlto mate thmt

o $ P ~ B E I B abillS 91 QPHMBB ten8 t o nave ltha em@

varlua a f t,, 1CC fmduenoioa jmt @eebhear to mt OP

selmaCloa, the yah6. being C 3 at $be lsweaft teaperatwe

W & P Z W @ W ~ * ~ ddl ~~d~(~f#nd&lbl .@* @dZ%b@ s);t $h@80

Orra~upualaoiem Wa cranb~kbutiantl Bo c ,, erierpua frm the

in4uord 4ipclY.e aommt; ~tllm$ %be 100$ &if thO 11o1s~uX%e

and laduead as wrU aaa p o r ~ l i ~ m o dllg@3elsr ~efpoRdl0~1Jr

t o tb 1 ~ 3 ~ are# i*qrea, 4.6 rrrd 4=7).d9 !Rhola@ aorrtri- blrtiam ere pracaMaallg tha e m i n tb twe ompaun8s.

Howrvsr, f a the ~ 8 ~ ~ 1 6 QP I1

&&her l~&iecld t o PJ $3 WHI at, beglSsak Co beormee agsrln

*a the long; rsXaxe8 as we dtaauatwed earllor.

By plo$tin& la wafagh 1/3? whr)a'@ fE $8 the

re2rwatllon irequsnay corrrrpaabtnlg t o %he mxianr~r in

e:: an& 9 Dlra ~ b 8 0 f ~ O b 01180ge~~hf0 )~ we s b f s*tni@hli

&Axas $rap&& Sn Wke B and A pbbels. pr8 sRwa Zrr iig.4*25

fox 1 t PWmlf, lmhi l a %he A phwa 0.t 1 1 ESPHeBI?) an&

12 OP-rn [2.1@8. 4.26 an8 4.27 seapealAraly). E M

ar@arursmn%@ ~euL4 ~ 0 % be aodlr Sa M a W p R m of %toe

hhCm $wo aonrgoudr~a, baosium af $ha very 8h63r% rmge t a i

~xlatcrpac os %ha% ~ h @ @ t s Sn Paw tb craau (%able 4.l) .

%%rt @lager o f We 31wa Kive t h acrafva.e;lrra QBC)EIJ&@@

whJhPorh are Xistc~8 Zn B&bXb 4.3 i es a3.1 Obi$ thxraa oor~prr~8s sBullLad* ? t S ra Pnferaractfw t o neBa WlrO rtte

m%tvation emr&,y i~ia ~ o * l a o r l l ~ r tCPIa law ih Wa A phases

a&' b@$k 11 GPWQM .%at% 11 PB(OQC;BB, !The apoOiratlon

~NSBY i s %n a s r pha~aa thnn i n PS pharaa (r9

1 1 ZPPeQtBB* The Pa#sr *r@uS1 Ba@ bars $@as3 c)mlArs

l a aaamral atudire *orta~r@und& sxbibi$tngl barn ;h and

& plalrrs.8. "Pe aaate+ord&atern snmigy l a a isrum o f bo%h

ttke ro0ortitonal. p$ten%ial bofsk'lcr agelnst fSipgSng about

%hr arhwt u i 6 and df*:alpatL@a due $10 t9;h fr&ot&aa

8oaIiiafrnt &%oh 90 rffecit im RuOZP IL r~)tatl@mBL1

4ifZirsion. Penso lib lovsrkng o i tihe WM;i*&Uen emra

FIGURE 4.22

Plot of in fR against I/T in the smectic A and nematic phases of 11 PMaOCBB, where fR is the relaxation frequency . The arrow mark indicates TAN*

FIGUIIE 4.26

Plat of In + against I/T in the ~lmectllo A phase of 11 CPMeOBB, whore % i a the relaxation frequency.

FIGIRE 4.27 ----.--

Plot of i n 912 against I/T in the smectic A phase of 12 CPMeOBB, -.vnrhorc frt is the relaxation frequency.

i n 8he A p h u e i s rc~wwhaO puodio& or sn, wtruld -UI

snpecrt $ha$ at lowti Ohe e~leata0iamr2 po$e~drlcb2

bar.tior orauld be M@er clue t o m e hlLgh@x wdw y e r r r -

aetie]: tn fhe A phase. Wuen on6 w~~~reniex~' &rra

rrrguetl $hat la Qhe care of bilarrdlr c~artobioa $hat &be

erscsrrgy ow?te ao fmc$ion o f that ~ g l e betwew O h e i x .

long are. (f&g.4.2&). Ptlay oaeured $hat i a frhe P pturrre

*e uynuortwy wwl4 diaarppear? (i.b., Ya Wb). m 6h6 A p W 6 we lrmrlng 30 nvgporrad t o bring $a We

m m e $ x y euah that WsA> UHk a M W i P < %as Zf WSA da

very nuoh j ~ l ~ w t ~ x tfran Wh* Qne aan erpaat %ha% f re

eas.trartrual field wllX no$ be ssbl.e t o diafuab Cha ~ o l e c ~ u l a r

p d r e i a We rslrrtl2arallol. ocbstfisurafian (f.bb,, wiOh

uurw a& @a&$ ths ~oXeouX*@ In %be jmr&Xl*1

aonffgux&l;;too C w i t ? i 6atafZlaX ~sz .%@r WAA) wm1B perti-

~ i y r ~ t o fen IBhs rwt;nnSrslrt;i%&on. &m i t a6 arp-4 Z r b C kid,,(

Ph@ a~uoatian aaaargy i s ; rower& i a %la A phorerr.

;WW*VQX, w mwt paLnOl a@% Q*~irtO Z t i s ualtkrallg *hat ghe

~imi.osQrogr;g & the po0sna9,21 arxmarrgy ~113, v e m h i a lrha

8 pbee. b o a ss;rsl ra~reinjsz~s w & ~ ~ r s B sL2LZ hal&@

i f tm &dbni@~$xt;ple~~ Ph tihe t.t7n phanrea a m eucah %ha%

W! <\riI. BA Zo ~ t h ~ x + WQX&@, the Z d j a ~ ~ ? l 3 l g 55 f ha A ghooe

IRlslpa t o &q$gq@ .t;he ~aig~irdfL-Oca tnt~araa@$ rJm badwean

ayrm5 oard &w$l~ at' /h&r&a256~5 n;olil?nuXew.

FIGURE 4.28 v---

Schematic diagrwr~ depicting the vurintton of loca l energy of a pair of highly polar molecules a s a function of the angle between their long axes (Reproduced from ref . 33).

h r f t b l e X ' , bhd X @ W ~ ~ W b9f 190$&Q@fiO31 BWFOB;I I%

fmnd no* oaly fa B$layex amotlcl a phaaer bsfd a&a@

in monolayr*" a n e a ~ a r r ~ ' in uMch the potaratiol aamgg

suatt~otropg i r a Zikely 40 bar q&tb au~&Zk. Banua the

wigin cf the pharuoII6II)on i r $9 be sought in *he Layare4

w ~ m * w n t @I? lhe A aphad* A4ae2I. Zn a f i ~ ZEP1Xowf w parcawapkra, WE wilI try t o argue 4hsa6 trwo dfilerent

me@hanlmrs@ 0.0 ba sssrpwlb.ble for thfa efieeb.

96 8rsodiatb 39fw~i.r.18 and Xarb4.a "lava p m p o ~ e b a

&bye ~e -a t i aa $&a@ a,, %a xeh&a%At;iOa 2~3%chr

oawrd bl %be nssm\ELtio potenblral an8 fnfrcbuaea by

b i e r and #aupatg aa & a e u s W ewlier, ssll ii,, fkus

g$&$& &leleo$ric aorrsaanlr parPitleJ t o *a, direotolr

ulid sr Cha aeaun dte lee t r io o~@Wn.l i* Cwm it%

brsaka)~ aars mw i n tb$a tiwaxy d o e ltpm irk#

alpale 0@2=2olsIcsmg f n the mdluai. We w~lseuers Shall

roXertion (4.8) oaa rtr use4 Pn $he A phaer &so. !&to

layexing eil b h . A pha#e d v a e r & ~ % Cc i m ~ e a e r d &&if-

gar~rlX%l dlgsJa owxslaatlonr krtweea the Zong a t e

@onapagsnts off di3oloa. har been iomd elcprrl-

lxesnttalZj for sewwax oourrse, includivys xeTca;S;lraly ww*aUIy

y a h r aorapo~~.&s. "?7*M*39 XMerd audr ~omefa t loar r

reed So a frrwertng o f s , u , the uPamperafua'e 18 dsereaeed

la irhs A p h r o as we c3m a#!m i r o a il&s,4*4 and 4.7-4.'llie

02% tho ofher ha&, l o a l l Bhwe oaeea, a,,

Wie IP phase d#t lowoxUg o f t m s p r x a ~ r o ~ Z B I D IP lpX.

$10101 T ~ X I ~ X Q I I (4.8) %hie nuwe %Rat effro.bfvre2y Uro

mwe raapidly v i a 4 6 8 ~ ~ 0

ol bd)DI;)errptt\~ %n the 1YI ghwo man &hati &IV@'CSIIL by the

ra%atdia.t;San laa tor g,, alone. %!he opprtpo@ita teapcbr~ltu~ro

wazlrtioa of? t,, la t h e A pbmo XeBLaa t o low s,,

t a l u ~ a i n %the a gbnue tbzn lia L?l@ 8 y b # e ar%n a,, t s eh~racr%errlte$ by $he ~18181 po*ent;lral b&rrAar Q i n OR0

twa phur06. %%us the ParyerSng order prsraerit i n th6

X gWlre @tee s i e r $o s 1 @ ~ . t f D Q a4 t,# 01 aq,uivt~X,$ntly

a M&er v~~lw@ EP;F the i ! r e~~~*rny ~f rel8xa$iim, Plrrt;hex,

a@ the tepqeza%we i r a Satwwed &n tho A phwo, tihe

rnrelsU a ardor g

alaa inweasah %We i r obtiaulslp evn&veildsnt 8e @a

loweriw o i t h e osc+~ivetloo @xrerr&,y 80 oaa be aoea, foe

a=pkr her fig 4*23. Xa ~~~r, M. e f i ~ b e l .the

(a , , - 1) t e r a i n eu~atAdn (4.8) i a $0 laamc~eo the

aativr.klon eaerg~t fa the I p h e e a d l e w r it i n the A

phaaa, thuar leadiag t t p a asomlduc&ble di ffermods Sn %he

aotivi~atPea e ~ x g i e s of! @do phwe8.

We rSL#o beliavr Bblat a nroonl mehanlem m y

olpamto ;in O;h@ r gh*ae due to paakbpg raifeotar, A8 ur

dlaouelred eaar2ias i n akaptw LXX. %he tbesre;l ezpansim

Ln trhe A plaaae appmzu ta be oamsiderabfy aaisoWopio.

UauallJ the ZryPrr eugaofnpt &me a& nfd l rnwb with

temrpaarar.ture i n monoXager @m@%ieo@, f n We s b ~ aS

bulky XrtwcS rrubattJ*(Iata f a Wiia mt~teoulsm. A liquid

i a known t o bards ' to ld@' or 'holiaos' in l t e rr.0rwatucr.

QIQl orn orgslcrl t r i ~ ~ t r t.he wlparfia phabe haua a sparuallg

uniflw~b QistiribuUaa of %he *holest. tihe tmmiCforr

t o the A 6-0 gXo@$, me fXlStdity b e ~ ~ l ~ ~ a ~ m f l n e d

t c the layers. Benav ahe b o l ~ a @an br exp~atad tcs ?M

ta?ap@.d #he layer*. Coaee?luen$ly hlr* nuubax of

aoZllstoas dbr4 r r c l b c ~ l e rufiwar i n the rsaPrlentw

ClowX mourn aaa; ba ~mlrllur la the & @ h a s M @or *he

mrcrluraPfan tfme @an be 1 1 0 ~ er efb..utiv8*ttlg* &a pro91-

t s U o a e e x ~ oouz b8 Souex thaa i n Oh8 Y p h u s ort ?ha

saar, Bentgilry* Por W P ~ i n o e , Waf& l ffaa* m y b6 izagor-

fan$ i n 4-m-sotg30tpkcryortlabipb~X (iEl QOEr) w M o h

axhlbitaa c b i L a g * ~ A pkaae wA%h hnsd&y 4smercnfure

depesdeaoe o f the Lap* ~ p ~ r a ~ ~ r " @ 8GrX3 oleo axhAblOe

r l ~ w e t o~Pi fa tS~d. ewxgy $he & phm8 ?ha Ln We I

plursa (ohapbss Pf 1. !the plsouclftg *ffwCi arry anglaln

*he etiwUer obwermtim nrf fwe arstimtioa egeratea i n

t t OPW~EIB aa~l 12 Q P ~ B " ti"tm. 4r.H 4.30)* u W*

na?aQ il)arXler in Ohap0dba X X f , %are Icrwounde ham rr

aan$rao.kiaa @f 9hn layer ~paatag i n ?he Lwoz ha@rrata\m

sang* aka A phbearg bat pn w& srh higher +eslpa-

rarlutrra (ram flea. f .20 and 9.21). orrraSt~raea energg*

i n miha two as&onra: &a dkhs$5rrolZty grQBiferllaat, ]Lower i n Phs 3wex ?brnflxahzs e. lager arprneriaa i n

%he hi&gi.r %earpetaturre raw* weald fap2fp ma? B M tkarauj

oxpwcpiaa l a pore iacatxo~lo Sn $hi@ rmga a d thus t h e

paaklng (rite~~liie r ma14 $2~6 aafivratloa srutrgpr

a.p)rnp;ore& th$ i n the lowx ?al~porta%~m r w e bran

aopsgh it 16 a t j l l f plm2frsr ohm Wara of the ?# pbae.

FIGURE 4.29

Plot of relaxation frequency ( fR) against 1 /T for 11 CPMBB. T, i s the normal nematic-smectic A transition temperature. T2 is the smectic A - reentrant nematic transition temperature, (Reproduced from ref . 32).

Plot of relaxation frequency (fR) against I/T for 12 CPlrIBB. TI i s the normal nematfc - mect io A transition temperature, T2 is the smectic A - reentrant nematic transition temperature.

(Reproduced from ref. 32).

o w e of l i PE(eBBuBB the layeah mp&olw$ tnorraser oomrpt-

der'rpbxy W i a tamp(oSatWer But \sr OW.%% .bntJt SZuW %he

lnflu6noo sf $hi@ fZgroZo~ on the aot lvot lon emr&es.

Pfut long a l e oop~polseat a f $ha d&pdle nmxr0 l a r o low

nsarwatl.

f n oonulurrlora, obnges taking phraoe t n tb, bihyex

a%matusas of attanf?;lp. yokr oempoukrfa are i o W t o ham

a profound itai'lwnca on $heir dial@crtxPo p r o ~ ~ ~ l l t l e @ .

X t bha dipo2e oroarantla ef the llnkaigr moup opposa Ohat

of t he t a rmlml pohrr group and %Re awqpounds have bulky

l a t r o a l aubrtlbmenfe, 'Ibbssg polaaeear b/larysr abuc tusee

with large b i b g n s a p r o i w wh&& are oxtremly ramrlttve

$0 Oeqeratuse and @an axhfbl* mvee@srl s f b e bleroa&ng

negaffve at lawekv t@lslpex&?tuce. %%a@. Wsngea i n the

bllaty6grex eb;rruo%ure we raPlre%sd i n *be c ~ l h x a t i o n proaear

rho. lrQz inakunca, th* pa& r ~ r l u e C& bn 1 t PMm

inomaaas wi ah inareas ln$ tsarperrraWs t b u ~ h one waul4

aom8XTy expeot an oppoaitr twofill andl showa a b ~ m d

mlax~aOl on at iv 6 PRs whiQb 1 as a r e l a t i v a y le*r f~eqluoaay

gas the relaxa%lon i n bhLa dirao%ion* &~~lrfhe~, $he

ina=e:..ed antfperorXXrJ c ~ ~ m l a 9 S a s l Sn the isryered 1 phorar cb

@omp%xed t o thil) ghPeo wad %ha poaa~ble ,anleotropy i n

the ospaanlon ooeffioi~nnt aS %he h y w 0 4 A plhanee ajeQear

60 give a loweo &aBlalva$isn earrgy ier lib raw

fi?.gu*ncy dioleoOrio r'a&axa$Lea @it r ,, in bhe A ghrle

thrrn in %ha ld pbee. horfhex in*@atiwttaa* a m

msriuwrt far a k%9*k wdwshanding of &a wahaRiarr

Xeodlnab. to tho low*rirttc rrS arcrtiv~rttee, energy in tihe

A phae than in Me ~8 ;pb*aro.

a ~ , r r . a e ~ e ~ , SOTM 4lfi&+e E L ~ ~ I O A Q B . ~ulgpi. ~ o . 1 4 , Eb, L.htebrrli, goadetltc Prersa, Eaku Xurk (1978) p.109~ see .loo W.8, 4e Yew, B ~ Y O T I Q B I , P E Q P O S ~ ~ ~ B of LIyrrid * r a $ a W c ~ HtitnfelfelFierla, QoPd~n & Breaeh, Pew ~ O F L ( I M O ) .

7 R.'P.kdhuaudam, Blg.S;iadaerh:va and Y.P,b.Moodithaya, aUrc.rrOS. &, 615 (95793.

W.F&er -8 @.MOT, &.B&Wl*fwas~R~ u, law ($561)"