Liquid Crystals of Disc-Like Molecules

There were theoretical prediction and experimental indication that assemblies of dick-shaped molecules might exhibit thermotropic liquid crystals. The first experimental observation that the pure single component compound hexa-alkanoyloxybenzoate exhibits liquid crystallinity was made in the year 1977. This was the landmark discovery in the history of science of liquid crystals. This discovery opened a whole new field of fascinating liquid crystal research. However, it is well accepted that disc-shaped liquid crystals cannot compete with their calamitic counterparts in terms of electro-optical performance. It is also true that their unique structural and electronic properties have opened completely different aspects of possible applications in topical research field such as molecular electronics and high-efficiency organic photovoltaics. Thus, in recent decades, the subject of disc-shaped liquid crystals has received considerable attention. On the basis of structure and symmetry they have been broadly classified as discotic nematic, columnar and lamellar mesophases. This chapter deals with the structure, design and synthesis, alignments, and properties of mesophases exhibited by disc-shaped molecules.