OPTICAL-ACTIVITY IN THE SMECTIC-A PHASE OF A HIGHLY CHIRAL LIQUID-CRYSTAL

Optical-activity measurements in the smectic-A phase of various chiral-racemic mixtures of S-4-(2'-methylbutyl)phenyl-4'-n-octylbiphenyl-4-carboxylate (CE8) demonstrate that contributions from fluctuations in more than one chiral structural mode are important near the transition to the smectic-C* phase. Although these results are similar to earlier measurements in the isotropic phase of highly chiral liquid crystals, previous theoretical work points out that the nature of these fluctuations and the reason for the importance of the second structural mode are very different. Because the present measurements are reported on mixtures of varying chirality, they provide a stringent test of the theory. Agreement between theory and experiment is good.