POLYMER-SILICA HYBRID MATERIALS PREPARED FROM SOME FUNCTIONALIZED POLYBENZOXAZOLES AND POLYBENZOBISTHIAZOLES

Hybrid organic-inorganic composites were prepared by precipitating sil ica into hydroxypolybenzoxazole (HPBO) and sulfopolybenzobisthiazole ( SPBT) polymers, with interfacial bonding between the phases improved b y use of isocyanatopropyltriethoxy silane and N,N-diethylaminopropyltr imethoxy silane, respectively. The materials were transparent, and sca nning electron micrographs indicated a uniform distribution of silica particles of domain sizes less than 1 mu m. Values of the tensile modu lus and tensile strength of the HPBO-silica composites were found to i ncrease with the silica content. Values of the modulus of the SPBT-sil ica composites also increased in this manner, but the improvements in tensile strength were nearly independent of the amount of silica. The composites exhibited thermal decomposition temperatures of approximate ly 400-550 degrees C, and the thermal stability was significantly incr eased for both HPBO and SPBT materials with increase in silica content . The water absorption amount for both types of composites decreased s ignificantly compared to that of the pure polymers, suggesting excelle nt weatherability.