Resorufin-Catalyzed PhotoATRP Under Red Light

The sodium salt of resorufin (RSF), an inexpensive, water-soluble, commercially available phenoxazinone dye, serves as an efficient photocatalyst for low-copper dual-catalysis PhotoATRP across the visible spectrum. RSF loadings as low as 1 ppm catalyzed PhotoATRP of acrylates in the presence of CuBr₂/Me₆TREN, yielding polymers with low dispersities (Đ ∼ 1.07) and high initiation efficiencies. Control was maintained under blue, green, orange, and red irradiation. The living character of the system was confirmed by linear first-order kinetics, light-on/off temporal control, chain extension, and molecular weights that tracked targeted degrees of polymerization up to 1200. The system was also effective for the ATRP of oligo(ethylene oxide) methacrylate (OEOMA₅₀₀) in aqueous media using CuBr₂/TPMA and was tolerant to residual oxygen. Fluorescence-quenching experiments identified oxidative quenching as the predominant pathway for photocatalytic activator (re)generation.