Polymerization of vinyl acetate using visible radiation and a dye-reducing agent sensitizer: 2. Kinetic studies and polymerization mechanism

The polymerization of vinyl acetate photosensitized by ethyl eosin and ascorbic acid in aqueous methanol shows a marked induction period before polymerization commences, but thereafter, irradiation does not affect the rate of polymerization. Both dissolved oxygen and water are essential for polymerization, and the rate passes through a maximum as the concentration of dye or reducing agent is increased. A mechanism for the reaction is proposed involving initiation of polymerization by hydroxyl radicals. Polymerization initiated by reaction between hydrogen peroxide and ascorbic acid is also studied as this system is thought to participate in the photochemical system.