Correlation between Molecular Orientation of Side Chain of Alignment Layer and Liquid Crystal Monolayer Studied by Surface-Second Harmonic Generation

Abstract

The second-harmonic generation (SHG) intereferometry has been applied to determine the phase of SHG from an SH-active side-chain polyimide (PI) alignment layer with SH-active liquid crystal molecules evaporated on it. The phase difference between SH waves from the PI layer and from that with evaporated LC molecules monotonically increases with the increase of the evaporation time, while the SHG intensity turns to increase after an inital decrease. These two facts indicate a picture that LC molecules are adsorbed with an antiparallel polar orientation with respect to a polar side-chain orientation. The usefulness of this method to study the orientational relationship between an alignment layer and a LC monolayer on it is pointed out.