Synthesis and Photoinitiated Cationic Polymerization of Organic−Inorganic Hybrid Resins

A streamlined synthetic scheme was developed for the preparation of a novel series of cationically polymerizable epoxy-functional organic−inorganic hybrid resins. The reaction sequence consists, first, of the regioselective rhodium-catalyzed monoaddition of an α,ω-Si−H difunctional siloxane to a vinyl epoxide. The second step involves the addition of the remaining Si−H bond of the latter adduct to vinyl trimethoxysilane. Finally, an ion-exchange-catalyzed sol−gel hydrolysis of the resulting trialkoxysilane-functional epoxide yields the desired silicone−epoxy resins bearing pendant epoxy groups. These resins undergo facile UV and thermally induced cationic photopolymerization in the presence of onium salt photoinitiators to give cross-linked organic−inorganic hybrid glassy matrixes. The mechanical and thermal properties of the polymerized resins were determined and were correlated with the structures of the resins.