Determination of Molecular Inclination in Rubbed Polymer for Liquid Crystal Alignment by Measuring Retardation

Abstract

Liquid crystal molecules on a rubbed polymer alignment layer are aligned at some polar angle away from the surface, but the physical reason for this pretilt is not yet clearly understood. In our research, we have developed a new method to determine the tilted direction of the polymer by a precise measurement of the optical retardation using Senarmont ellipsometry. Using this method, we also studied the tilt angle of the polymer molecules near the surface of a side-chain polymer layer as a function of the rubbing strength and compared the pretilt angle of the liquid crystal to the tilted direction of the polymer.