Thermodynamic, electrical and electro-optical features of the racemic mixture of an antiferroelectric liquid crystal suitable for displays

Abstract

A detailed investigation of the thermodynamic, electro-optical and dielectric characteristics of the racemic mixture of an antiferroelectric liquid crystal has been carried out. The material has phase sequence of I-SmC-SmCA-Cr. Due to racemic mixture, system is achiral but SmCA has anticlinic structure. The studies show that the racemic mixture possesses a wide temperature range (~98.0–86.7°C) SmC and (~86.7–8.0°C) SmCA phases. The switching parameters are determined in the SmCA phase by the polarisation reversal method. Effective macroscopic and saturation polarisation, switching time, and rotational viscosity have been determined. Switching times of the racemic mixture are one order greater than those of the non-racemic antiferroelectric materials. The dielectric studies have been carried out in the frequency range of 1 Hz to 35 MHz under planar anchoring conditions of the molecules. The dielectric spectrum of the SmC phase exhibits one relaxation mode and that of the SmCA phase exhibits two relaxation modes. Relaxation frequencies of these modes lie in the range of kHz–MHz regions. In the SmC phase, Goldstone mode could not be observed due to achiral nature of the mixture.