Theory on the Contribution of Head-Tail Asymmetryof a Molecule to the Phase Transitions in Chiral Smectic Liquid Crystals

Abstract

A chiral rod-like molecule has the head-tail asymmetry, so that the pair potential between such molecules in head-to-head configuration is naturally different from the potential of those in tail-to-tail or head-to-tail configuration. Taking the head-tail asymmetry into account, we propose a simple model of chiral smectics and calculate the free energy of possible phases in a mean field approximation. The results show that the head-tail asymmetry can contribute to stabilize certain type of antiferroelectric phase between the ferroelectric smectic-C^* phase and the antiferroelectric smectic-C^*_A phase.