Hybrid of Organophotoredox- and Cu-Mediated Pathways Enables Atom Transfer Radical Polymerization with Extremely Low Catalyst Loading
Qihui Ti, Liping Fang, Libin Bai, Han Luo, Rui Sun, Xinwu Ba, Weiping Chen
Abstract
The rise of photoredox catalysis has extended the landscape of reversible-deactivation radical polymerization. Recently, visible-light-driven photoredox/Cu dual catalyzed atom transfer radical polymerization (photoATRP) has become an emerging trend, providing well-defined polymer under low copper catalyst loading. In this work, we described a dual catalyzed ATRP using CuBr 2 /tris(2-pyridinylmethyl)amine (TPMA) and donor–acceptor-type organophotoredox catalysts (OPCs) with visible light absorption. The excited state OPC can reduce both dormant polymer chain-end and CuBr 2 /TPMA, generating propagating radical species and CuBr/TPMA, respectively. This indicates that the mechanism is a hybrid of organophotoredox-mediated and Cu-mediated ATRP. The photoATRP driven by 425 nm light irradiation produced a series of well-defined polymethacrylates under extremely low catalyst loadings (5 or 10 ppm CuBr 2 and 1 ppm OPC relative to monomer). The method also showed excellent temporal control over polymerization and oxygen tolerance.