Twist inversion in a cholesteric material containing a single chiral centre

Abstract

A novel liquid-crystalline material, S-2-chloropropyl 4′-(4″-n-nonyloxyphenylpropioloyloxy)biphenyl-4-carboxylate (902C13T), which undergoes an inversion of helical-twist sense in the cholesteric phase, was prepared and its physical properties were investigated. The behaviour of the pitch and the twist sense of the helical structure in the cholesteric phase are reported. It is suggested that the helix inverts because of changes in the populations of conformational isomers, and that these changes are temperature dependent. An equation that was originally formulated to account for an inversion in the sign of the spontaneous polarization (P_s) in certain smectic C* materials may be adapted for the modelling of helix inversions.