Optical and Dielectric Anisotropy in Polyimide Nanocomposite Films Prepared from Soluble Poly(amic diethyl ester) Precursors

Optical and dielectric anisotropy of the polyimide nanocomposite films prepared from soluble poly(amic‐diethyl ester) precursors has been studied using a prism coupling technique. The composite films showed nonlinear dependence of in‐plane and out‐of‐plane refractive indices (dielectric constants) on the composition. Consequently the in‐plane dielectric constant of the composite films was not much reduced owing to the still high in‐plane orientation of the rod‐like polyimide, leading to the quite high dielectric anisotropy.