Observation of Surface Nematization at the Solid−Liquid Crystal Interface via Molecular Simulation

Abstract

We report molecular simulations of a model liquid crystal that evidences the existence of surface phase transitions when its vapor is placed in contact with an unstructured attractive wall. Monte Carlo simulations are performed in the grand-canonical ensemble on a wide pore at a range of temperatures corresponding to states below and above the bulk nematic-isotropic-vapor triple point of a Gay-Berne fluid. At bulk coexistence conditions, the system exhibits complete wetting of the vapor-wall interface either by nematic (low temperature) or isotropic liquid (high temperature). There are no hints of a thin-thick prewetting transition, but a surface nematization of the first fluid layer close to the substrate; that is, a surface phase transition between a disordered film and a nematic-like film is observed. The nature of the ordered film is studied and is shown to be analogous to the transition seen on a two-dimensional Gay-Berne fluid and persists even at the highest temperatures studied, corresponding to isotropic liquid bulk conditions.