Dynamic Responses of Ferroelectric Liquid Crystal Mixtures Doped With Nano Materials

Abstract

This thesis has been divided into seven chapters. Chapter 1 reviews the basic features and classification of liquid crystals (LCs) in general and ferroelectric liquid crystals (FLCs) in particular. The various electro-optic structures of FLCs are described in detail. It also includes a brief discussion on research works already accomplished by various research groups in the area of nano dispersed liquid crystals (nDLCs). The objectives of present research work and the future scope have been described at the end of the chapter. Chapter 2 deals with the basic dielectric and electro-optic relaxations present in the FLCs. A review of non-collective re-orientation and the collective polarization mechanisms in the SmC* phase of LCs has been discussed. Theory of electro-optic transmission and contrast is given. Chapter 3 presents the experimental design and characterization techniques to study the various nDFLC composites. A detailed description about high precision and standard measurement equipments is also given. In Chapter 4, we present experimental results based on the dispersion of silica (SiO2) nano particles in a room temperature FLC system. The thermo-optic, dielectric and electro-optical responses of SiO2-FLC composite films have been studied in detail. Various relaxation modes were observed. The effects of SiO2 concentration on the spontaneous polarization, tilt angle, threshold voltage, driving voltage, optical transmission contrast ratio, switching time and rotational viscosity were also examined with temperature and voltage. In Chapter 5, we prepared the multiwalled carbon nano tubes dispersed FLC composites by ultrasonication technique. The nanotubes were functionalized with COOH group before dispersion. The investigations on textures, colour switching, dielectric studies and electro-optic studies as a function of applied voltage, temperature and CNT concentration are given. Chapter 6 we have made an effort to synthesize nickel nanoparticles by chemical reduction method of a nickel salt. The characteriza