A Molecular Field Approach to Pressure Induced Phase Transitions in Liquid Crystals : Smectic-Nematic transition

TL;DR

This paper develops a molecular field model to analyze pressure-induced phase transitions in liquid crystals, specifically focusing on the smectic-A to nematic transition, incorporating effects of molecular interactions and external pressure.

Contribution

It introduces a modified mean field potential based on Maier-Saupe theory to better describe smectic-nematic phase transitions under pressure.

Findings

Dependence of phase transition on coupling coefficient between order parameters

Existence of a tricritical point in the phase diagram

Variation of entropy and specific heat with pressure

Abstract

Since a rigorous microscopic treatment of a nematic fluid system based on a pairwise interaction potential is immensely complex we had introduced a simple mean field potential which was a modification of the Maier-Saupe potential in a previous paper. Building up on that here we have modified that potential to take into account the various aspects of a smectic A-nematic phase transition. In particular we have studied the dependence of the phase transition on the coupling coefficient between the nematic and smectic order parameters which in turn depends on the length of alkyl chain, existence of tricritical point, variation of entropy and specific heat as well as the dependence of the phase transition on pressure.