Photo-induced controlled radical polymerization with new Photocatalyst

Photo-induced electron transfer reversible addition-fragmentation chain transfer (PET RAFT) of methyl methacrylate (MMA) was investigated at 25 °C with rose bengal (4,5,6,7-tetrachloro-2′,4′,5′,7′-tetraiodofluorescein) (RB) as photoredox catalyst under visible light irradiation. The traditional chain transfer agent 4-cyanopentanoic acid dithiobenzoate (CPADB) was employed in this study. The kinetic curve of the photo-induced PET RAFT polymerization exhibited a good linear behavior. The number average molecular weights (Mn,GPC) of the poly(methyl methacrylate) (PMMA) increased linearly with respect to monomer consumption and they were in good agreement with the calculated values (Mn,th). At the same time the molecular weight distribution (Mw/Mn) was narrow. Temporal control of PET RAFT polymerization of MMA was demonstrated by “ON/OFF” experiments. The resulting PMMA was characterized by 1H–NMR, and GPC. The resultant PMMA could be used as macro-chain transfer agents for the PET RAFT radical polymerization. The chain experiments were successfully carried out and the living characteristics were demonstrated. The probable mechanism was discussed.