Photo-induced cobalt-mediated radical polymerization of vinyl acetate†
Well-controlled poly(vinyl acetate) (PVAc) was successfully synthesized by photo-induced cobalt-mediated radical polymerization using (2,4,6-trimethylbenzoyl) diphenylphosphine oxide (TPO), which is commercially available, cheap, easy to store and has a high initiation efficiency, as the initiator in the presence of Co(acac)2 under UV irradiation (65 μW cm−2 at 365 nm) at 30 °C. The polymerization showed characteristics of living polymerization behaviors, such as linear kinetics, the molecular weight of the polymers linearly increasing with conversion, and the obtained polymers had a narrow molecular weight distribution. The polymerization can reach high conversions with a controlled manner (>80%, polymers with a molecular weight distribution in the range of 1.1–1.4) after a short induction time. Polymers with molecular weights as high as 120 000 g mol−1, with a narrow molecular weight distribution, were obtained. The mechanism of the polymerization was proposed based on the polymerization behavior and polymer structure.