Liquid Crystals Research Paper

INTRODUCTION

Liquid crystals (LCs) are those matter in which has properties between conventional liquid and those of solid crystal.[1] For example, a LC might flow like a liquid, but its molecules may be oriented in a crystal-like way. There are many different types of liquid-crystal phases, which can be illustrious by their different optical properties (such as birefringence). When seen beneath a microscope through a polarized light source, different liquid crystal phases will appear to have distinct textures.

Liquid crystals can be divided in to 3 distinct type- thermotropic, lyotropic and metallotropic phases. In which thermotropic and lyotropic liquid crystals consist of organic molecules. As temperature is changed, thermotropic LCs show a phase transition . Lyotropic LCs show phase transitions, as a role of both concentration and temperature of the liquid-crystal molecules in a solvent (usually water). Metallotropic LCs are formed by both inorganic and organic molecules; and it’s liquid-crystal transition depends not only on temperature and concentration, but also on the inorganic-organic composition ratio.

we can called the cholesteric phase since it was first experiential for cholesterol derivatives. Only chiral molecules can provide such phase. This phase exhibits a slanting of the molecules vertically to the director, with the molecular axis similar to the director. This restricted twist angle between neighboring molecules is due to their asymmetric packing, which consequences in longer-range chiral order. The molecules have positional ordering in a layered structure (as in the other smectic phases), in the smectic C* phase (an asterisk denotes a chiral phase), with the molecules tilted by a finite angle with respect to the layer normal. The chirality induces a finite azimuthally twist from first layer to the next, producing a spiral twisting of the molecular alliance beside the layer