Orientation Orders of Small Anisotropic Molecules in Confinement

Abstract

We have studied orientation‐ordered transitions of small anisotropic molecules in confinement based on standard constant‐pressure Monte Carlo molecular simulation. These molecules are modeled by the hard Gaussian overlap (HGO) model with a small elongation parameter. Two different confining geometries (slit pores and mixtures of HGO) are studied, which confining surfaces are composed of two hard parallel plane and the molecular surfaces of some large HGO molecules, respectively. In both cases, there is no attractive interaction between the confining surfaces and the small molecules which favors the orientation alignment. We found, although the small HGO molecules cannot form stable orientation‐ordered phases in bulk due to their too small molecular elongation, a liquid‐crystal (LC) phase form in the nanometre‐scale confinement. It means that the required molecular elongation for forming LC phases will decrease in confinement. Our obtained result implies that small anisotropic molecules might show liquid crystal behavior in confinement.