Twisted Conformation of Molecules of a Chiral Banana-shaped Liquid Crystal Indicated by Polarized FT-IR Spectroscopy

Abstract

Achiral banana-shaped molecules exhibit a tilted polar smectic phase, the B_2 phase, composing of two types of layers having opposite layer chirality. As the origin of this spontaneous symmetry breaking, the conformation chirality of the molecules which originated from the twist conformation of molecules was suggested. In this experiment, the polarized FT-IR measurements were carried on a planar aligned domain of SmC_AP_F^* phase of a chiral banana-shaped mesogen, P8OPIMB6^*. The absorption intensity of each C=O peak exhibits different angular dependence when the polarized direction of IR light is rotated. The simulated angular dependence gives similar profiles to the experimental result when two carbonyl groups tilt to the same side with respect to the central phenyl ring plane, respectively.