Mesomorphic state, classification

The basic classification of "Liquid-Crystals" is divided into two major groups the thermotropic and lyotropic. In the first case the structure is modified from the crystalline state to the amorphous liquid, passing trough the "Liquid-Crystals" state as the temperature is increased in the second case the order related to the crystalline texture is decreased trough the non ordered amorphous structure as a solvent is added to the crystalline materials. In both cases the adjective mesomorphic refers to the occurence of the new state of matter in the range of stability interposed, for a particular compound, between that of the crystalline type, which prevails at low temperature or in the pure state, and that of die amorphous type which, in turn, is found at higher temperatures or in diluite solutions. 

Second, the ability of completely aromatic polyesters to form mesomorphic structures is interesting. Obviously, in such cases, the appearance of nematic LC states seems most probable. Furthermore, some polybenzoates (3-8) show mesophases, which cannot be described in terms of the conventional classification of liquid crystals, with respect to their arrangement, and which are similar to mesomorphic structures of flexible-chain polyorganosiloxanes (9) and polyphosphazenes (10). Finally, studies of relaxations and phase transitions in rigid-chain LC polyesters, in particular, their molecular mobility in the solid state, i.e., below the melting temperature of crystalline phase, are of great interest. 

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