Morphology and thermo-mechanical properties of compatibilized polyimide-silica nanocomposites

Polyimide-silica nanocomposites have been prepared from an aromatic polyamic acid derived from pyromellitic dianhydride and oxydianiline and a silica network using the sol-gel reaction. Compatibilization of the two components was achieved by modifying the silica network with imide linkages. Morphology, thermal, and mechanical properties of these composite materials were studied as a function of silica content and compared with the one in which reinforcement of the polyimide was achieved using a pure silica network. There was considerable reduction in the silica particle size with more homogeneous distribution in the matrix when imide spacer groups were introduced in the silica network. The tan 5 spectra obtained from dynamic thermal mechanical analysis shows a large increase in the glass transition temperature with increasing silica content for the compatibilized system in contrast to the un-compatibilized one. Mechanical properties of the polyimide composites improved due to better interaction between the organic and inorganic phases. (c) 2005 Wiley Periodicals, Inc.