Photoinduced Electron Transfer-Reversible Addition-Fragmentation Chain Transfer (PET-RAFT) Polymerization of Vinyl Acetate and N-Vinylpyrrolidinone: Kinetic and Oxygen Tolerance Study

Photoinduced electron transfer reversible addition fragmentation chain transfer (PET-RAFT) polymerization was employed for the polymerization of unconjugated monomers, including vinyl acetate, vinyl pivalate, N-vinylpyrrolidinone, dimethyl vinylphosphonate, vinyl benzoate, and N-vinylcarbazole, in the presence of low concentration (ppm range) of photoredox catalyst, fac-[Ir(ppy)(3)], under low energy visible light irradiation. Kinetic studies of vinyl acetate indicated excellent control of molecular weights and molecular weight distributions (M-w/M-n = 1.09-1.2), even with high monomer conversion (>75%), in different catalyst concentrations. High molecular weights of poly(vinyl acetate) (M-n > 100 000 g/mol) and poly(N-vinylpyrrolidinone) (M-n > 40 000 g/mol) with low dispersities (M-w/M-n < 1.25) were obtained in bulk polymerizations. Moreover, the online kinetic study using Fourier transform near-infrared (FTNIR) showed comparable kinetic rates for the polymerizations in the absence and presence of relatively large amount of air, which demonstrates that the PET-RAFT technique possesses the ability of tolerance toward oxygen. Successful chain extensions of homopolymers of poly(vinyl acetate) and poly(N-vinylpyrrolidinone) to vinyl acetate and vinyl pivalate confirmed their integrities of end-group S-(S=Z)-O.