Sign Inversion of Induced Molecular Tilt in Chiral Smectic A Liquid Crystals

Abstract

We have observed a peculiar sign inversion of the field-induced molecular tilt with respect to the layer normal in the smectic A phase of some chiral compounds as temperature increases. At a characteristic temperature, the electroclinic response of the system to an external electric field completely disappears, and thus in turn, the induced molecular tilt vanishes. This unusual behavior can be understood in terms of a dynamically fluctuating mixture of at least two molecular conformers, separated by an energy barrier in their liquid crystalline state. It is suggested that these two conformers are associated with the rotation of normal hydrocarbons in the compounds.