Equilibrium phase behavior of polymer and liquid crystal blends

A theoretical framework describing the equilibrium phase behavior of polymers and liquid crystals is presented. Linear and crosslinked polymers are considered, and complexities found in the phase properties of systems involving crosslinked networks are highlighted. Effects of the rubber elasticity parameters in the elastic free energy are found to induce substantial distortions in: the phase diagram. The Flory-Huggins interaction parameter which governs the miscibility of the mixture in the isotropic state is assumed to be independent of the polymer architecture and modeled either by using a function of temperature only or temperature and composition. The thermodynamic description of the ordered domains is made according to the Maier-Saupe theory for nematic order and its extension to include other ordering properties. In particular, the smectic-A order is described according to the generalization of the Maier-Saupe theory proposed by McMillan. III the presence of nematogens, the coupling leads to quite different phase properties. In the strong coupling limit, a wide single nematic phase is found. In the weak coupling, the miscibility gap is much wider. These mixtures are described with mean-field theories of nematogen first developed by Brochard et al. and later extended by Kyu et al. This theoretic formalism has been applied successfully to analyze data obtained on several systems including linear and crosslinked polymer networks, smectic and nematic low molecular eight liquid crystals (LMWLC), and nematogen mixtures.