Evidence for two coexisting nematic phases in mixtures of rod-like and disc-like nematogens

Abstract

We have studied the phase diagram of mixtures of two nematogens one made up of rod- like and the other of disc-like molecules. The N-I transition temperature drops sharply as the second component is increased from either end of the phase diagram, indicating that the two types of nematics are not quite compatible. As the temperature is lowered, in composition ranges with a large molar fraction of the rod-like compound, there is a coexistence of two nematic phases. This observation, which is first of its kind for such mixtures, is in broad agreement with the result of a recent theoretical model put forward by Palffy-Muhoray et al. The nature of the phase diagram appears to be strongly influenced by excluded volume effects.