BEHAVIOR OF HELICAL PITCH IN CHOLESTERIC AND CHIRAL SMECTIC C-STAR PHASES

Several nonchiral liquid crystals exhibiting nematic and smectic C phases have been doped with different chiral compounds. The handedness and the pitch of the induced helical structures were determined in both phases. Whereas some chiral dopants induce helical structures which, as to be expected, possess the same handedness in all matrices and phases, we found that in some cases the same dopant induces helical structures of opposing handedness in different nematic matrices. Moreover, it was observed that the helical sense in the chiral smectic C* phase can be opposite to the helical sense in the chiral nematic phase of the same liquid crystal system. The dependence of the helical structures on the composition was studied in several quasi-binary diagrams.