Optical anisotropy of polyimide
Article first published online: 10 MAR 2003
Copyright © 1990 John Wiley & Sons, Inc.
Journal of Applied Polymer Science
Volume 41, Issue 9-10, pages 2049–2058, 1990
How to Cite
Nakagawa, K. (1990), Optical anisotropy of polyimide. J. Appl. Polym. Sci., 41: 2049–2058. doi: 10.1002/app.1990.070410911
- Issue published online: 10 MAR 2003
- Article first published online: 10 MAR 2003
- Manuscript Accepted: 13 DEC 1989
- Manuscript Received: 22 AUG 1989
Optical anisotropy of polyimide films prepared from polyamic acid solutions was investigated by conoscopic observation and refractive index measurements. The conoscopic figure (crossed pattern) characteristic of a negative uniaxial crystal with its optic axis perpendicular to the film plane was observed for samples imidized on substrates. Uniaxial drawing of a polyamic acid cast film with 40 wt % solvent gave a highly oriented sample with an elongation of more than 80%. This sample had a conoscopic figure characteristic of a positive uniaxial crystal with its optic axis equivalent to the molecular c axis (parallel to the film plane). A large optical anisotropy (bire-fringence 0.18) was observed in the film plane. The TE-mode refractive index (parallel to the film plane) ranged from 1.64 to 1.82 at a wavelength of 633 nm according to the sample rotation. These values corresponded to the refractive indices perpendicular and parallel to the c axis, respectively. The optical system change of the polyimide film was explained in terms of the uniaxial orientation of the in-plane oriented molecular c axis.