Boundary Dependence of the Formation of New Phase at the Isotropic-Nematic Transition

Abstract

The phase separation of a mesogen-nonmesogen mixture was studied with particular emphasis on the effects of boundary conditions imposed at container walls such as rubbed polyvinylalcohol (PVA) film, obliquely evaporated SiO film, free surface, etc. Microscopic observations revealed that the equilibrium shapes of a nematic or isotropic liquid formed on a substrate in the temperature range of isotropic-nematic coexistence vanes greatly depending on the nature of the substrate. Typically the contact angle of a nematic liquid formed at the isotropic-substrate interface is 0° on a rubbed PVA film and at the free surface, and is nearly 180° on an Sio film. The connection between the substrate induced ordering and the contact angle is discussed.