POLYIMIDE-SILICA HYBRID MATERIALS MODIFIED BY INCORPORATION OF AN ORGANICALLY SUBSTITUTED ALKOXYSILANE

Polyimide-silica hybrid materials were prepared by the in situ polymerization of tetramethoxysilane in a polyimide precursor (poly(amic acid)), which was subsequently cyclized at high temperatures. An organically substituted alkoxysilane, (aminophenyl)trimethoxysilane (APTMOS), was included to provide bonding sites between the polymer and the silica-like phase. The APTMOS was chosen for its high thermal stability (comparable to that of the polyimide) and its ability to undergo hydrolysis and polycondensation along with the tetramethoxysilane. These sol-gel reactions thus form ceramic-like domains having amino groups that can react with the carboxylic acid groups on the polyamic acid at elevated temperatures. Relatively small amounts of APTMOS were found to improve the modulus and strength of these hybrid materials, and their transparency was found to increase with increase in amount of APTMOS. The thermal decomposition temperatures they exhibited were approximately 570-degrees-C, and their residual weights after exposure to 800-degrees-C were directly proportional to their inorganic contents.