ON THE PHASE-TRANSITION OF SMC(A)ASTERISK LIQUID-CRYSTALS

A simple microscopic model of the antiferroelectric SmC(A)* liquid crystals is proposed so as to analyse a few possible phase transitions between smectic subphases with various macroscopic dipole moments. It is theoretically implied that SmC(A)* liquid crystals show a universal phase sequence SmC(A)* (Antiferroelectric), SmCgamma* (Ferrielectric), and SmC* (Ferroelectric) with increasing temperature in general. This is considered as a consequence of a competition between an attractive dipolar interaction and an excluded volume effect which results in a packing entropy related to the steric hindrance between the biaxial molecules. Also the effect of an external electric field on the phase transition is investigated.