ABSTRACT:Polyimide-silica hybrid materials with covalently bound phases were prepared via a sol-gel process. The starting materials were p-aminophenyltrimethoxysilane terminated poly(amic acid)s of controlled molecular weight ranging from 5000 to 10000 g mo! -1 and tetramethoxysilane. Optical transparency of the final films increases with the number of bonds between phases. The dependence of the thermal and mechanical properties and morphology on the silica content and/or concentration of bonds between phases were studied.