Free Radical Induced Acceleration of Cationic Photopolymerization

Two new monomers based on α-terpineol were prepared, allyl α−terpineol ether epoxide ( III ) and 1-propenyl ether α-terpineol epoxide ( IV ). The photoinitiated cationic polymerizations of these two monomers as well as two model compounds, 1-propenyl α-terpineol ether and methyl α-terpineol ether epoxide, were studied using real-time infrared spectroscopy. Surprisingly, the rates of epoxide ring-opening polymerization of both monomers were greatly enhanced as compared to the model compounds. At the same time, the rate of polymerization of the 1-propenyl ether groups in IV was depressed. Two different mechanisms which involve the free radical induced decomposition of the diaryliodonium salt photoinitiator were proposed to explain the rate acceleration effects.