Photosensitized polymerization of vinyl acetate under high pressure

By use of the rotating sector technique under high pressure, the changes which occur in the rate constants of the propagation and the termination reactions in the polymerization of vinyl acetate, photosensitized with azocyclohexane‐1,1′‐dicarbonitrile were studied at 30°C over a pressure range of 1 to 1000 bar. The effects of pressure on the individual rate constants were determined and the activation volumes of propagation and termination were obtained as −24,0 and 16,3 cm 3 mol −1 , respectively. The effect of pressure on the propagation reaction of vinyl acetate was somewhat larger than those of styrene and methyl methacrylate, and the termination rate constant showed a smaller decrease with pressure than those of the other vinyl monomers, especially of methyl methacrylate. The problem concerning the differences of the pressure effect on the termination reaction is discussed from the view point of the chain transfer reaction to monomer.