Polyimide-silica hybrid materials were prepared via a modified sol-gel, high pressure-thermal polymerization procedure. Precursor monomer salts were made from ethanol soluble 2,5- diethoxycarboxyl terephthalic acid (p-PME) and either a disiloxanediamine, an aliphatic diamine (1,9 diaminononane) or combinations of the two. Solutions of tetramethoxysilane (TMOS) and monomer salt were transformed into a gel, dehydrated, and the resulting powders were subjected to high pressure and thermal polymerization and transformed into a polyimide-silica composite. By varying the TMOS content, and/or the siloxane to aliphatic diamine ratio., composites of 0 to 100 wt% SiO2 were made. The silica morphology changed significantly with siloxane/aliphatic PI ratio. Reaction mechanisms, thermal and physical properties and composite morphologies are discussed.