title: Controlled Photoredox Ring-Opening Polymerization of O-Carboxyanhydrides.
abstract: Poly(α-hydroxy acids) are important biodegradable polymers with wide applications. Attempts to synthesize them from O-carboxyanhydrides with pendant functional groups by various methods, including methods involving organocatalysts or organometallics, have been plagued by uncontrolled polymerization, including epimerization for some monomers, which hampers the preparation of stereoregular high-molecular-weight polymers. Herein we describe an effective protocol that combines photoredox Ni/Ir catalysis with the use of a Zn-alkoxide for efficient ring-opening polymerization, allowing for the synthesis of isotactic polyesters with expected molecular weights (>140 kDa) and narrow molecular weight distributions (Mw/Mn< 1.1). Mechanistic studies indicate that the use of a low temperature (-20 °C) and photoredox Ni/Ir catalysis synergistically accelerates ring-opening and decarboxylation of the monomer for chain propagation while avoiding the formation of the undesired Ni-carbonyl complex.
authors.affiliation: Center for Molecular Systems and Organic Devices, Institute of Optoelectronic Materials, Key Laboratory for Organic Electronics and Information Displays & Institute of Advanced Materials, Jiangsu National Synergetic Innovation Center for Advanced Materials, Nanjing University of Posts and Telecommunications , 9 Wenyuan Road, Nanjing 210023, China.|Department of Chemical Engineering, Virginia Polytechnic Institute and State University , 635 Prices Fork Road, Blacksburg, Virginia 24061, United States.
authors.forename: Quanyou
authors.initials: Q
authors.lastname: Feng
authors.affiliation: Department of Chemical Engineering, Virginia Polytechnic Institute and State University , 635 Prices Fork Road, Blacksburg, Virginia 24061, United States.
authors.forename: Rong
authors.identifier: 0000-0002-2034-9272
authors.initials: R
authors.lastname: Tong