Dielectric and Spontaneous Polarization Studies of a Ferroelectric Chiral Smectic Liquid Crystal

Abraham K George,C Carboni,D M Potukuchi,W M Zoghaib,S H Al-Harthi

doi:10.4236/wjcmp.2012.22013

Abstract

Dielectric relaxation and spontaneous polarization studies have been carried out in a low molar mass organosiloxane liquid crystal, TSi10PPBN4 which displays a wide temperature range of de Vries Smectic A* and chiral Smectic C* phases. The temperature variation of the permittivity and dielectric loss studied are found to have anomalous variations in the vicinity of the phase transitions. The frequency variation of permittivity and dielectric loss are also studied in the de Vries Smectic A* and Smectic C* phases. The relaxation frequency, fR is found to decrease with decreasing temperature. Temperature variation of fR is found to follow an Arrhenius shift from which the activation energy is estimated. The thermal variation of the spontaneous polarization, Ps is measured using the polarization reversal technique in the Smectic C* phase. Ps increases initially, reaches a peak value and then drops drastically in the vicinity of the SmC*-SmA*de Vries phase transition.

Highlights

Amongst the wide variety of experimental methods used to study the molecular dynamics of liquid crystals (LCs), the low frequency dielectric spectroscopy assumes special importance due to the utility of the relevant data in electro-optic devices
The tilt angle in the Smectic C* (SmC*) phase with respect to the smectic layer normal is considered as the primary order parameter, while the spontaneous polarization is considered as the secondary order parameter
We report the results of the dielectric and spontaneous polarization studies carried out in a monomeric low molar mass organosiloxane liquid crystal material, viz., TSi10PBN4 which exhibits wide temperature ranges for SmA*de Vries and SmC* phases

Summary

Introduction

Amongst the wide variety of experimental methods used to study the molecular dynamics of liquid crystals (LCs), the low frequency dielectric spectroscopy assumes special importance due to the utility of the relevant data in electro-optic devices. These LC devices are known to operate in the frequency region of a few Hz to several MHz that involves different modes of their molecular motions. The key point in their application is exclusively based on our understanding of their molecular motion in response to an applied field As they belong to the class of thermotropic LC phases, it is important to study the influence of temperature on the underlying orientation order (like the C* tilt angle and the spontaneous polarization Ps) in the liquid crystalline phase of devise interest. The data obtained from dielectric and optical studies provide a further directive for the preferred design and synthesis of FLC material with an optimized performance

Results

Discussion

Conclusion