Elasticity and Orientational Order in Sometrans-p-n-Alkoxy-α-methyl Cyanophenyl Cinnamates

The splay (k 11), twist (k 22) and bend (k 33) elastic constants determined by the Freedericksz method and the orientational order parameters (s) derived from optical measurements in the nematic phase of six homologues of trans-p-n-alkoxy-α-methyl cyanophenyl cinnamates (n OMCPC) are reported. The data close to the nematic-isotropic transition point (T NI) are compared with T NI and the heats of transition (ΔH). The temperature-variation of elastic constants is discussed in terms of existing theories. The pretransitional increase in the twist and bend constants near the nematic-smectic A transition point (T NA ) of 10 OMCPC has also been analysed.