Study of different modes of dielectric relaxations in antiferroelectric liquid crystal MOPB(H)PBC

Abstract

Dielectric spectroscopy of the ferro- and antiferro-electric phases of an antiferroelectric liquid crystal namely [4,4-(1-methyloctyloxycarbonyl)phenyl]-4'-[3-(butanoiloxy)prop-1-oxy]biphenyl carboxylate (MOPB(H)PBC) has been carried out in the frequency range of 1 Hz to 10 MHz. Typical behavior of soft mode relaxation in SmA* has been observed. Two-dielectric relaxation modes: FM1 (Ferroelectric mode 1) and FM2 (Ferroelectric mode 2) have been recognized in SmC* phase. The relaxation frequencies for FM1 lie between 2 and 25 Hz and those for FM2 lie around 3.5 kHz (Goldstone mode). Also two dielectric relaxation modes AFM1 (Antiferroelectric mode 1) and AFM2 (Antiferroelectric mode 2) have been observed in antiferroelectric SmCA* phase. AFM1 lies between 3 and 10 kHz and its relaxation frequency decreases with decrease in temperature. AFM2 lies above 400 kHz but the temperature dependence of its realization frequency is opposite to that of AFM1.