NEW ORGANO-SOLUBLE POLYIMIDES FOR OPTICAL, MICROELECTRONIC AND FIBER APPLICATIONS

A novel class of organo-soluble polyimides has been developed based on monomers containing twisted-biphenyl structures. Thus, 2,2'-disubstit uted-4,4'-diaminobiphenyls and 2'-disubstituted-4,4',5,5'-biphenyltetr acarboxylic dianhydrides have been prepared and polymerized in refluxi ng phenolic solvents. The polyimides, some of which are soluble in ket one and ether solvents, can be readily solution cast into colorless th in films. The rigid polymer chains align parallel to the substrate sur face (in-plane orientation) during the casting process, which results in anisotropy in the film properties. The anisotropy in the refractive index has been used in the development of compensation layers for liq uid crystal displays. The polymers have also been dry jet-wet spun fro m phenolic solutions to afford fibers that display tensile strengths o f 3.5 GPa and moduli of 130 GPa.