External Regulation of Cobalt-Catalyzed Cycloaddition Polymerization with Visible Light

Coordination polymerizations have been extensively used in commercial plastic and rubber industries since 1956, because of their ability to produce polymeric material with well-defined structure, tunable molecular weight (M-n), narrow dispersity (D), and useful chain ends. Typically, these processes are initiated by chemical reagents that sacrifice temporal and spatial control of catalysis. Recent advances in photoredox catalysis have sparked an emergence of photocontrolled ionic and radical polymerizations; meanwhile, photocontrolled coordination polymerizations remain relatively unexplored. Herein, we report a light-regulated cobalt-catalyzed [2+2+2] cycloaddition polymerization. Using this methodology, block copolymers are generated while regulating their M-n with visible light.