Phase Diagrams of Eutectic Mixed Systems with Monotropic Liquid-Crystalline Phases

Abstract

Abstract The phase diagrams of three different eutectic liquid-crystalline systems with monotropic transitions have been investigated by differential scanning calorimetry (DSC) as well as by polarization microscopy. In all systems the monotropic transition becomes enatiotropic as a function of composition, because of the intersection of a phase equilibrium line with one liquidus line. Consequently, a horizontal phase equilibrium line occurs which separates two two-phase regions. The special features of these complicated phase diagrams are discussed and experimentally verified. In the case of systems with more than one mesomorphic phase, the high temperature mesophase again appears in the low temperature two-phase region. This effect may simulate a reentrant behaviour of liquid crystall line systems.