Photoinduced atom transfer radical polymerization (ATRP) was successfully achieved under visible light LED irradiation using specific transition metal complexes including L/CuBr2 or L/FeBr3, or organic photoredox catalyst in a metal-free manner. A TPMA/CuBr2 catalyst was used under 392 nm LED irradiation to polymerize oligo(ethylene oxide) methyl ether methacrylate (OEOMA) in water. Polymers of OEOMA were synthesized with low dispersity (Mw/Mn : 1.12) using 22 ppm of L/CuBr2 catalyst in the presence of excess Br anions in highly diluted (90 vol%) aqueous media. Moreover, in photoinduced Fe-catalyzed ATRP, well-controlled polymerization of methacrylate monomers was obtained by using ppm FeBr3 catalyst (100-200 ppm) under a blue LED (450 nm). Polymerizations were conducted in the presence of Br anion as ligand to yield well-defined polymers (Mw/Mn : 1.10-1.30). In the metal-free photoinduced ATRP, phenyl benzo[b]phenothiazine (Ph-benzoPTZ) was used as a visible light photoredox catalyst. The photoexcited state Ph-benzoPTZ photocatalyst under 392 nm LED irradiation was oxidatively quenched by alkyl halide initiators to form initiating radicals and photocatalyst radical cation. Control was achieved by deactivation of propagating radicals by the radical cation photocatalyst and bromine anions. Using visible light in these systems enabled temporal control over the polymerization by switching the light source on and off. High chain end functionality of the polymers was confirmed by chain extension reactions to efficiently form block copolymers.

Visible light-induced atom transfer radical polymerization

254th National Meeting (2017)

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