Matter exists principally in three distinct states -crystalline solid, isotropic liquid, and gas. Individual units in both the liquid and gaseous state are more or less mobile, while in the crystalline solid state these units are held in the rigid, three dimensional configuration of a crystalline lattice. Consequently, the crystalline solid is regarded as the most highly ordered of the three states of matter. Heating a crystalline solid increases the thermal vibrations and the ordered arrangement begins to break down. The solid passes from the highly organized crystalline state to the disorganized isotropic liquid. In 1888, Friedrich Reinitzer discovered that, on melting cholesteryl benzoate, the solid collapsed to form a turbid liquid which, on further heating, gave the normal, transparent, isotropic liquid.1 This turbid liquid exhibited properties of both liquid and crystalline forms of matter; the substance was both birefringent (a property of crystals) and fluid. Although Reinitzer is credited with discovering the liquid crystalline phenomenon, Lehmann2 was first to suggest the name "liquid crystals", and to describe their properties. Later, Friedel3,4 proposed the term "mesomorphs" or "mesophases" for substances that were neither isotropic liquids nor crystalline solids. Since both terminologies are generally accepted, the terms liquid crystal and mesomorph, or liquid crystallinity and mesomorphism, will be used interchangeably throughout this thesis
