The photoinitiated polymerisation of 4-methylene-1,3-dioxolanes

4-Methylene-1,3-dioxolanes can be polymerised via a cationic or free radical mechanism. In both cases there is a possibility that ring opening and elimination can occur following addition of the chemically active species to the methylene group. Use of real time infrared spectroscopy to monitor the polymerisation of these compounds using a photogenerated acid showed that ring opening occurred concurrently with disappearance of the unsaturation of the vinyl ether group. The reaction proved to be very rapid. The resultant polymers were characterised by gel permeation chromatography (GPC) analysis. When such a dioxolane is reacted with a thiol in the presence of a radical photoinitiator the vinyl group is destroyed but ring opening is not observed. Clearly, addition of a thiyl radical to the methylene generates a radical which reacts preferentially with the thiol by hydrogen abstraction rather than undergoing fragmentation. (C) 1997 Elsevier Science S.A.