ELASTICITY AND ORIENTATIONAL ORDER IN SOME TRANS-P-N-ALKOXY-ALPHA-METHYL CYANOPHENYL CINNAMATES

The splay (k//1//1), twist (k//2//2) and bend (k//3//3) elastic constants determined by the Freedericksz method and the orientational order parameters (s) derived from optical measurements in the nematic phase of sic homologues of trans-p-n-alkoxy- alpha -methyl cyanophenyl cinnamates (n OMCPC) are reported. The data close to the nematic-isotropic transition point (T//N**I) are compared with T**N**I and the heats of transition ( DELTA H). The temperature-variation of elastic constant is discussed in terms of existing theories. The pretransitional increase in the twist and bend constants near the nematic-smectic A transition point (T//N//A) of 10 OMCPC has also been analyzed.