Anthraquinones as organophotoredox catalysts for atom transfer radical polymerization via sequential absorption of visible light

Anthraquinones have been used as the organophotoredox catalysts to catalyze metal-free atom transfer radical polymerization (ATRP) under visible light irradiation. Polymers with different molecular weight and molecular weight distribution were obtained under different reaction conditions. The “living”/controlled nature of the polymerization was confirmed by the kinetic study, light on/off experiment and the block copolymer synthesis. The anthraquinones are found to catalyze ATRP via redox mechanism via sequential absorption of visible light. Evidence supported by control experiments showed that the excited anthraquinone radical anion or semiquinone anion generated by photo-induced single electron reduction or subsequent protonation and further reduction were responsible for the initiation/activation of the polymerization.