Circular Dichroism of New Twisted Smectic C Liquid Crystals Composed of Chiral Molecules

Abstract

It was found that several new types of chiral smectic C phases composed of chiral molecules exhibit CD (circular dichroism) with large CD magnitude. The observed CD band was discussed in terms of its helical sense and helical pitch, which are in good agreement with those observed by other optical measurements. The pitch band CD in its magnitude and in its wavelength depend on the temperature and the sample thickness, being due to change in the pitch of the phase. Especially, helical pitch variation in the liquid crystal composed of p-(hexyloxy)phenyl 4'-[(S )-2-methylbutyl]biphenyl-4-carboxylate was unusual and discontinuous at the transition temperature of cholesteric to smectic and vice versa. The CD technique provides a useful and powerful tool for the analyses on helical sense, helical pitch, and other twisted structures.