A well-defined, versatile photoinitiator (salen)Co-CO sub(2)CH sub(3) for visible light-initiated living/controlled radical polymerization

• Published in: Chemical science (Cambridge) Vol. 6; no. 5; pp. 2979 - 2988
• Main Authors: Zhao, Yaguang, Yu, Mengmeng, Zhang, Shuailin, Wu, Zhenqiang, Liu, Yuchu, Peng, Chi-How, Fu, Xuefeng
• Format: Journal Article
• Language: English
• Published: 01-04-2015
• Subjects: Block copolymers; Categories; Monomers; Nuclear magnetic resonance; Photoinitiators; Polymerization; Radicals; Sunlight
• ISSN: 2041-6520; 2041-6539
• DOI: 10.1039/c5sc00477b

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 sub(w)/M sub(n) < 1.2) were obtained under various conditions. The structures of the polymers were analyzed by super(1)H NMR, super(2)D NMR, super(13)C NMR, GPC, MALDI-TOF-MS and isotopic labeling experiments, which showed that the omega and alpha ends of the polymer chains were capped with (salen)Co and -CO sub(2)CH sub(3) segments, respectively, from the photoinitiator (salen)Co-CO sub(2)CH sub(3). The omega end was easily functionalized through oxygen insertion followed by hydrolysis from super(18)O sub(2) to - super(18)OH. This robust system can proceed without any additives, and offers a versatile and green way to produce well-defined homo and block copolymers.