Synthesis and characterisation of some discotic amphiphiles

Abstract

Self-assembly is the spontaneous organization of building blocks into ordered structures without any external influence. During self-assembly, the molecules organize through non-covalent interactions such as dipole dipole , van der Waals forces, hydrogen bonds etc (1); Liquid crystals are well known hybrid phases of matter characterized by the conglomeration of order as in solids and mobility as in liquids. They have been termed as fourth state of matter. Thanks to Reinitzer who initially observed this phase transition phenomenon in cholesteryl esters (2, 3) and termed it as double melting . Later Vorlander extended the study of these compounds and found them to be associated with both order and mobility (4). Thermodynamically all systems have a tendency to attain a state of maximum entropy with minimum possible energy. It is this balance of two opposing forces which form the basis for extent of order or disorder in a system. Crystalline solids usually possess ordered structures and the constituent molecules display both positional and directional order. Positional order refers to the uniform arrangement of molecules or building blocks. Directional order refers to the arrangement of molecules or building blocks such that their anisotropic axes are oriented in the same direction in space. In the case of liquids the molecules are distributed randomly throughout its bulk and they possess neither positional nor directional order. Liquid crystalline (LC) materials generally possess a degree of order intermediate to those of solids and liquids (5). The geometric shape anisotropy of the constituent moiety, interaction anisotropy and microsegregation of the mismatching molecular parts are elementary necessities for any substance to exhibit mesomorphism (6). Liquid crystalline (LC) systems always exhibit directional order and sometimes positional order too.