Synthesis of hybrid methacrylate-silicone-cyclohexanepoxide monomers and the study of their UV induced polymerization

The synthesis of two hybrid methacrylate-silicone-epoxycyclohexane monomers is described. These monomers were prepared by sequential hydrosilation reactions attaching first the 4-vinyl-1-cyclohexene 1,2-epoxide, using the Wilkinson catalyst, and then the allyl methacrylate in the presence of chloroplatinic acid as catalyst for the hydrosilation reaction. The reactivity of these monomers was evaluated by RT-FT-IR finding that the methacrylate groups can be photopolymerized concomitantly with the epoxide groups using only a diaryliodonium salt as photoinitiator, in air-free conditions. The addition of a free radical photoinitiator helps to overcome the oxygen inhibition when the radical photopolymerization is performed in air. The films obtained from these monomers were almost totally crosslinked with Tg's of 54 and 31 °C for EM2Si and EM4Si, respectively. It was found that the film made with the monomer with a longer siloxane chain exhibited a higher contact angle as a direct result of the higher hydrophobic surface.