Abstract
Epoxy/silica hybrid materials were synthesized by the in-situ sol-gel reaction from an epoxy resin and 3-glyci doxypropyltrimethoxysilane. The glass transition phenomenon of the hybrids became obscure and thus their thermal stability improved with the progress of the hybridization with silica. However, it is hard to prepare the clear in-situ hybrids because of generating by-produsts in the sol-gel reaction of this type.
So, polyglycidoxypropylphenylsilsesquioxane (Ladder type epoxy-SQ, LDESQ) was synthesized from a glycidoxypropyltrimethoxysilane (GPTMS) via an ordinary sol-gel reaction. The glass transition phenomenon was not observed in the cured LDESQ and thus the high glassy modulus was kept until the thermal decomposition temperature. The high thermal stability of the cured LDESQ is due to the low mobility of the ladder-like inorganic network chains. The cured system, however, was very brittle for the same reason caused by the ladder structure. To improve the brittleness of the cured resin system, LDESQ was blended with the double-decker type epoxy-SQ (DDESQ) which had large mobility in the inorganic skeleton structure. The fracture energy of the cured SQ was clearly increased with an increase in the content of DDESQ, keeping the thermal stability of the cured resins. Dielectric constant of the cured resin was decreased with an increase in the DDESQ content. The low dielectric constant of the DDESQ should be ascribed to the large bulkiness of the double decker structure.
