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An Environmentally Benign and pH-Sensitive Photocatalyst with Surface-Bound Metalloporphyrin for Heterogeneous Catalysis of Controlled Radical Polymerization

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journal contribution
posted on 02.10.2018, 12:50 by Ya Huang, Xue Li, Jia Le Li, Bin Zhang, Tao Cai
The implementation of photocatalysts for controlled/living radical polymerization upon visible light harvesting has emerged as a robust and powerful technique for the user-friendly synthesis of well-structured polymers with composition, spatiotemporal, and sequence control. Nevertheless, the incompatibility of present synthetic protocols with environmentally benign media, such as water, still poses a detrimental threat to their practical applications. In this article, the adoption of hPGM-ZnTPP hollow microspheres with pH sensitivity and excellent dispersibility in various reaction media, which are firmly immobilized yet accessible catalytic metalloporphyrin components as heterogeneous photocatalysts for the photoinduced electron/energy transfer-reversible addition–fragmentation chain transfer (PET-RAFT) polymerization, was demonstrated. Modulation of solution pH affected the performance of the catalysts, with the faster polymerization rate being observed in basic conditions rather than in acidic conditions. Besides, this strategy allowed the polymerization of a myriad of functional monomers to afford high polymerization yields and narrow polydispersities in different solvents including dimethyl sulfoxide and water, under a wide range of catalyst concentrations and without prior deoxygenation. By virtue of the robustness of hollow microspheres, multiple isolation and regeneration of the catalyst was accomplished through facile centrifugation with sustainable catalytic activity and negligible catalyst leaching, which in return largely mitigated or even eliminated the contamination and/or decomposition on the final polymer products.