Resorufin‐Catalyzed PhotoATRP Under Red Light

ABSTRACT 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 CuBr 2 /Me 6 TREN, 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 (OEOMA 500 ) in aqueous media using CuBr 2 /TPMA and was tolerant to residual oxygen. Fluorescence‐quenching experiments identified oxidative quenching as the predominant pathway for photocatalytic activator (re)generation.