On Thermal Anomalies Due to Phase Transitions in Doubly and Singly Reentrant Liquid Crystals, CBOBP and OBBC

Abstract

Differential thermal analysis experiments are carried out on two reentrant liquid crystals, CBOBP and OBBC, whose phase sequences are Crystal–S_A1–RN–S_Ad–N–I and Crystal–RN–S_Ad–N–I, respectively. The reentrant phase transition (RN/S_Ad) is accompanied by a significantly smaller thermal anomaly than the ordinary ones (S_A1/RN and S_Ad/N). S_A1/RN had a larger thermal anomaly than S_Ad/N. Comparatively strong temperature-dependence of the heat capacity is suggested in RN. All these findings support the picture of competing incommensurate smectic periodicities and the phenomenological optimum density theory.