Ls a r t 3 not mo&usw$ 2crg w oct-@rX13+ th

of ehkas LlrqI;afd sry@hXum e. l%Hmma@~

PIG. 1 : Preferred orientation of neighbouriry5 d lpo les in the end-on and br oadaide-on p o s i t i om. Y B ~ B P E ~ Because of the anisotropic shape of tho molecules, s i t u a t i o n I fs mch more important than XI in %he nena.t;ic sen;icture and there results a net ant ipara l le l correlation betwaen mighbouring d ipo les .

FIG. 2 : 2%he=tic d iag ram 02 antiparallel local lstructure in 5CB (and 7CBf resulting in a repeat d i ~ t a n c e dong the textiire axis of 1.4 tines thc molecular length (proposed by Leadbetter et iil, 1975).

( all) ,m [a + 5 AP <P~) 12 h E,, 9

utr- h Q w(2E + 1) is tib oJI i ry factor. 3 1 ;/(%a$)

&a ;pt~mSiaaa S f a d daatux, rx %b ~~~ pdh~;t.&&U%y,

f - 4 S P w - 21k~.pa9(28 + I ) , P tltLe ihaw~t;y, 14 t h amla-

tzu3ax!

Wsr &aaWwY @;9" f i b p ~ X w & m U % y at u pafea+%y.

hi p~ sin t)$ OOR pi -..

But

jubetitutily. Zos <vZ) (q ) fial aywr*i- (13)

i n the oquatlcau (14). *a cjet E, , a d atL

2 +&- <"-aA Bind coo a m ~ ~ > j 3

. (45)

of both zwaa%f tl -4 i ~ @ % x o p & ~ -m are d ~ d a t a 4 by

coo eij]) oi both nam-o and &&mo,p&a pww

ara p&ta%1S& as nuMw"Leu; 2/'%, irr I I w m # 3. "P 1-

xmge ordar g w m t s r r r < ~ ~ ( @ o a 01) ( ~ ~ ( ~ 0 8 GI)

m d Q) f&elBh l i m i t ) , O b qtaauf i;t haat at a@mIm't

M man table I, the rntto [%= - E)/%gI d ~ r ~ w w a 4~ d ~ ~ ~ c n w i a ~ i * So BAZIA~AE kt

PIG.4: Long r&ge order parameter ( p a ) as func t ioc of T / T ~ ~ 0- 0s- 2.

FIG.5: Long range o r d e r pararrieter (P4) as f u n c t i o n of T / T ~ ~ -j& dttferenk V ~ W A of Z.

a- FI6.6: Specific heat at constant volume Cv ae~fmction of T&=

#u d;ffenn\ udw a- Z.

Z P ~ ~ E O tha B~X&%Q hat Q, (Llm 6 ) at

oam+snt at &l t ~ ~ e a a * ~ anQ ACv - ths jump

in 01 a* &I * @#a I kkw-m i z l a

QCP (atBia~1fiBIBb Uat) t~ Ir5.# b* WqX) M VrzZ- PIU:

le m 3. i aim%Lar ed 1 ~ 0 ~ ~ B U f.asX% *or ~ x w ~ = & ~ u B

i3b232w tag ?he oya%m of? a r ~ u X m ? s-m.

'TG. 7: Theure t i ca l valuea of dielectric canatants as functi oars

' of UTIJI*

FIG.8: Xxperimenta values of dielectric c o n s f a t s for 4-&nobenoonitrile ( ~ a ~ r o d u c e d frm Schadt , 1972). c,, and E, refer to the values along and perpendicular to the opt ic axis of the ncnatlc mediun and is

t h e i s o t r o p i c value.

& S ck-a~wm~g o f %M %h~ss3sy i s *aC

asan di*IE~de~trio ~ o a ~ t P n t ii ~ h o u l d incrws by a ierr

pw a m t tsln 6- fsoo .l;lha o -60 *a: S I E I ~ ~ i o phauso

l34m-a *hs di.Lrrptim in ( P $ ( M ~ eij)> (" .hGLa

&as), 3). %Ma i a 2.ournd Bo ba %QC Q W ~ exparr-ntw

i n s strooq&;g posi.t;fva &atarA&.ls (acts flgurtt 8)

~ s m 9id a2, tm, 9m). VQW W-W

lqpr al $ f a ~ m ~ BfttSUeO'&i4&iB & ?a

FIG.9: Variation of mean die lec t r ic conrstznt of the

nematic and the i a otropic phaoes as function of (T - TNI).

Sd far ask Mag 4ka ~ W ~ F S tb& they ksam a

P,(oos Bj) @pa of Oorn in tho Xcmg potantimrf. V(5).

Wag upon thr &&@a cri J1, ths qptsts crpn a&&bA% oftha?

J f ) pheacrs. mqy horn iouad that ( J ~ / J ~ ) ~ 00.3, the w i t h

-ti@ phaer ,< .4 CX mar t o e ayu ton w i f h nop