Molecular Orientation of Rubbed and Unrubbed Polyimide Films Determined by Polarized Infrared Absorption

Abstract

We have determined the orientations of poly[ 4,4 ′ -oxydiphenylene-pyromellitimide] (PMDA-ODA) molecules in rubbed and unrubbed polyimide films ( ∼120 Å) on Si substrates by polarized IR absorption spectroscopy. We found that for rubbed films the polymer chains are oriented along the rubbing direction and are tilted up on average by 8.5° from the surface plane. We conclude that the polymer chain inclination induced by rubbing determines the tilt of the director of the bulk liquid crystal.