Synthesis and optical properties of polyimides

Polyimides are important industrial materials because of their excellent pr operties. They are extensively used in the electronics industry and have gr eat potential in the field of optical communications. In this article, we d iscuss the effect of the polyimide structure and the processing conditions on the optical properties. Both commercially available fluorinated polyimid es and polyimides synthesized in our laboratory were used in this study. Th e relationship between the extent of fluorination and the refractive index was studied, and it was found that fluorination reduced the refractive inde x as expected. Studies conducted on the structure-property relationship rev ealed that with the use of more rigid monomers for the polyimides, the poly imides could be modified to show a large birefringence. The extent of biref ringence depended on the composition of the polymer. In addition, the proce ssing conditions directly controlled the residual stress in the polymer fil ms. The residual stress was an important factor in inducing light scatterin g, which resulted in higher optical loss. (C) 2000 John Wiley & Sons, Inc.