Molecular orientation of polyimide films determined by an optical retardation method

We have determined the molecular orientation of very thin (several hundredA˚) polyimide films on quartz glass substrates by measuring their optical retardation as a function of the incident angle. The molecular orientation was determined by fitting the experimental results with the theoretical calculation. Since both the multiple reflection in and the anisotropy of the polyimide film cause retardation, we calculated the optical retardation by a transfer matrix method. Then we obtained the molecular orientation using the Vuksʹ relation. We also determined the molecular orientation of the polyimide films on Si substrates by IR absorption. Close agreement was obtained between the molecular orientations determined by the two different methods.