Transfer of the in-plane molecular orientation of polyimide film surface to liquid crystal monolayer

We have determined the relationship between the in-plane molecular orientations of a polyimide film and the liquid crystal (LC) monolayer in contact with it. A photoaligned film of polyimide, containing azobenzene in the backbone structure, was used, because its in-plane molecular order can be varied over a wide range without change in the morphology and the chemical nature of the film surface. The in-plane order parameter of the LC molecule was found to be almost equal to that of the polyimide backbone structure. This result shows that the molecular alignment of the LC monolayer is mainly induced by a short-range interaction between the LC and polyimide molecules.