STABILITY OF ANTIFERROELECTRICITY AND CAUSES FOR ITS APPEARANCE IN SMC-ALPHA-STAR AND SMC-A-STAR PHASES OF A CHIRAL SMECTIC LIQUID-CRYSTAL, MHPOBC

The smectic layer thickness and the switching behavior in MHPOBC have been studied as a function of temperature; SmC(alpha)* is a tilted phase and is antiferroelectric at least in the higher-temperature region but becomes ferrielectric with decreasing temperature. The gradual appearance of ferrielectric characteristics in SmC(alpha)* suggests the emergence of the Devil's staircase. To explain the antiferroelectricity in SmC(alpha)* and SmC(A)*, two types of molecular interactions are proposed: one is the interaction between the spontaneous polarizations in the neighboring layers which is effective in SmC(alpha)*, and the other is the pairing of transverse dipole moments responsible for the antiferroelectricity in SmC(A)*.