Abstract
Polyhydroxyimide was prepared by the reaction of pyromellitic dianhydride (PMDA) with 4,4-oxydianiline (ODA) and diaminophenol in dimethylacetamide (DMAc) as solvent. Polyimide-silica hybrid films were fabricated by the sol-gel process using tetraethoxysilane (TEOS). Coupling agent gamma-glycidyloxy-propyltrimethoxysilane (GOTMS), was used to develop interaction between the phases. Thermal and mechanical properties of the hybrids were measured and compared with the similar matrix without pendant hydroxy groups. Incorporation of silica enhances the mechanical properties of hybrids both at low and elevated temperatures. The glass transition temperature (T-g) measured from the temperature variation of tan d curves was found to increase with an increase in silica content in the matrix. The increase in T-g was found to be the highest for the hybrids in which the polymer chain was chemically linked through hydroxy groups with the silica network. The coefficient of thermal expansion was reduced greatly by the silica network linked to the PI chains. The results have been explained due to an increase in interaction between the phases in the presence of GOTMS.