Optical characterization of three‐dimensional surface and bulk anisotropy in high refractive index polymers

Abstract

Interest in the development of polymeric materials for high temperature, electronic and microelectronic applications has led to an increasing number of new polymers. Many of these polymers have complex organic ring structures and semirigid backbones, characteristics that have posed some difficulties for structural analysis. The purpose of this paper is to test and compare two practical nondestructive optical techniques, polarized optical microscopy and polarized refractometry, for the determination of three‐dimensional surface and bulk anisotropy in these advanced materials. The optical techniques are first tested on a series of optically homogeneous uniaxially oriented isotactic polypropylene films and then applied to the analysis of high refractive index Kapton (PMDA‐ODA) polyimide films. The study includes a test of the validity of the compensator method, including the effect of fringe jumping, the use of polymer retarders, and the tilting technique of Stein.