Volume Transition of Liquid Crystalline Gels in Isotropic Solvents

The equilibrium swelling and phase behavior of the side chain liquid crystalline (LC) networks in isotropic (nonmesomorphic) solvents has been investigated as a function of temperature. The LC networks swollen in di-n-amyl phthalate or di-n-butyl phthalate exhibit discontinuous volume transition driven by nematic ordering: The swollen isotropic gel is discontinuously transformed into the shrunken nematic gel at a characteristic temperature (T NI G). The transition temperature T NI G depends on the swelling solvent, and T NI G decreases as the degree of equilibrium swelling in the isotropic phase increases. The volume transition phenomena observed are satisfactorily described by a mean field theory for nematic gel.