Phase separation in mixtures of thermotropic liquid crystals and flexible polymers

The spinodal equation and the concentration-induced anisotropic-isotropic transition equation of the mixtures of thermotropic liquid crystals and flexible polymers have been studied by using the molecular field theory. The calculations of the phase diagrams of this system show that, besides the isotropic classic spinodal curve, there exists an anisotropic spinodal curve which has not been reported in literature. These two spinodal curves can be linked up by the concentration-induced anisotropic-isotropic transition line. In the various phase regions, demixing may take place due to different phase separation mechanisms. The phase equilibrium curve cannot always join the spinodal curve at a critical point. These results are considered very meaningful for the understanding of the special properties of liquid crystal/polymer composites and very useful for controlling the morphology and the performance of PDLC materials.