A well-defined, versatile photoinitiator (salen)Co-CO

A well-defined organocobalt salen complex (salen)Co–CO2CH3 is used as a versatile photoinitiator for visible light-initiated living radical polymerization.
The control of the polymerization of a wide range of monomers under mild conditions by a single catalyst remains a major challenge in polymer science. We report a versatile, well-defined organocobalt salen complex to control living radical polymerization of different categories of monomers, including acrylates, acrylamides and vinyl acetate, under visible light irradiation at ambient temperature. Both household light and sunlight were effectively applied in the synthesis of polymers with controlled molecular weights and narrow polydispersities. Narrowly dispersed block copolymers (M w/M n < 1.2) were obtained under various conditions. The structures of the polymers were analyzed by 1H NMR, 2D NMR, 13C NMR, GPC, MALDI-TOF-MS and isotopic labeling experiments, which showed that the ω and α ends of the polymer chains were capped with (salen)Co and –CO2CH3 segments, respectively, from the photoinitiator (salen)Co–CO2CH3. The ω end was easily functionalized through oxygen insertion followed by hydrolysis from 18O2 to –18OH. This robust system can proceed without any additives, and offers a versatile and green way to produce well-defined homo and block copolymers.