Preparation and properties of organosoluble polyimide/silica hybrid materials by sol-gel process

Organosoluble polyimide/silica hybrid materials were prepared using the sol -gel process. The organosoluble polyimide was based on pyromellitic anhydri de (PMDA) and 4,4'-diamino-3,3'-dimethyldiphenylmethane (MMDA). The silica particle size in the hybrid is increased from 100-200 nm for the hybrid con taining 5 wt % silica to 1-2 mu m for the hybrid containing 20 wt % silica. The strength and the toughness of the hybrids are improved simultaneously when the silica content is below 10 wt %. As the silica content is increase d, the glass transition temperature (T-g) of the hybrids is increased sligh tly. The thermal stability of the hybrids is improved obviously and their c oefficients of thermal expansion are reduced. The hybrids are soluble in st rong polar aprotic organic solvents when the silica content is below 5 wt % . (C) 1999 John Wiley & Sons, Inc.