Helical Sense and Pitch of Cholesteric Liquid Crystals

The rotatory sense of a circularly polarized light transmitted through a cholesteric liquid crystal cell was studied by measuring the retardation of a birefringent plate placed upon the cell. Furthermore, the dependence of helical pitch on composition is described for various binary cholesteric and nematic-cholesteric mixtures. The helical sense of eleven cholesterics was determined by the experimental results. As a result, it is shown, for example, that cholesteryl chloride has a right-handed helical structure and cholesteryl propionate has a left-handed helical structure.