Electro-Optical Studies on Monotropic Nematic-Smectic Phase Transitions

Abstract

The formation of nematic phases which are monotropic either with respect to a smectic A or to a smectic B phase was shown to be possible both for binary mixtures of low molar mass liquid crystals as well as for unmixed systems. The existence of these monotropic states was demonstrated experimentally by means of electro-optical Kerr effect studies. The phase diagrams of such systems are characterized by the fact that the transition temperatures vary continuously in mixtures and in homologeous series as a function of the composition or of the chemical structure, respectively. This holds even if the nematic phase becomes monotropic with respect to a smectic phase.