Organocatalyzed atom transfer radical polymerization(O-ATRP)is a pivotal technique for the synthesis of polymers with well-defined structures that are devoid of metallic residues.A major challenge in this area is the ...Organocatalyzed atom transfer radical polymerization(O-ATRP)is a pivotal technique for the synthesis of polymers with well-defined structures that are devoid of metallic residues.A major challenge in this area is the reduction of catalyst loading while maintaining precise control over polymer architecture and properties.Herein,we systematically evaluate the efficacy of six pyrazino[2,3-f][1,10]phenanthroline(pyzPhen)-based photoredox catalysts in photoinduced O-ATRP.Experimental results indicate that the introduction of various substituents markedly influences the photophysical properties and redox behavior of the catalysts,thereby resulting in differing catalytic efficiencies in the O-ATRP of methyl methacrylate(MMA).Following additional optimization,two highly efficient O-ATRP photocatalysts capable of exhibiting thermally activated delayed fluorescence(TADF)were successfully identified.Under visible light irradiation,TADF catalysts effectively mediated the controlled polymerization of MMA at a low loading level of 50 ppm,particularly when used in conjunction with the initiator DBMM.The catalytic systems demonstrate excellent temporal control,broad monomer applicability,and favorable compatibility with various initiators and solvent systems.This work offers new insights into the development of efficient,low-catalyst-loading,metal-free ATRP systems.展开更多
Development of highly efficient organic photocatalysts(OPCs)is imperative in the advancement of photoinduced atom transfer radical polymerization(photoATRP).Herein,we reported a class of OPCs consisting of(difluoro)qu...Development of highly efficient organic photocatalysts(OPCs)is imperative in the advancement of photoinduced atom transfer radical polymerization(photoATRP).Herein,we reported a class of OPCs consisting of(difluoro)quinoxaline acceptor units,and diphenylamine donor unit.Ultrafast femtosecond transient absorption(fs-TA)spectroscopy revealed that the photoexcited OPCs formed charge-transfer triplet(3CT)states via intersystem crossing.Well-controlled photoATRP was developed by using sub-ppm(parts per million molar ratio relatives to monomer)level of these OPCs.Furthermore,the photoATRP in sealed vials were tolerant towards a substantial amount of molecular oxygen,exhibiting accelerated polymerization rate after an inhibition period.Mechanistic study elucidated that two kinds of reactive oxygen species,superoxide(O_(2)^(−))_(3)and singlet oxygen(1O_(2)),were concurrently generated by photoinduced electron transfer and energy transfer,respectively,from the 3CT state of OPCs.The oxygen in the reaction system was consumed via the reaction of oxidize solvent by 1O_(2).展开更多
Substantial progress has been made over recent years in visible light-driven dual photoredox/copper catalyzed atom transfer radical polymerization (photo-ATRP) through the design of photocatalysts (PCs) and the optimi...Substantial progress has been made over recent years in visible light-driven dual photoredox/copper catalyzed atom transfer radical polymerization (photo-ATRP) through the design of photocatalysts (PCs) and the optimization of reaction conditions. However, it remains challenging to achieve efficient photo-ATRP with low loadings of both photocatalyst and copper(II). In this study, two donor-acceptor organic PCs based on pyrazino[2,3-f][1,10]phenanthroline were successfully used to achieve efficient Cu(II)-mediated photo-ATRP. These organic PCs exhibit excellent visible light absorption capabilities and thermally activated delayed fluorescence (TADF) properties. Under blue light irradiation, the PCs facilitated highly efficient and oxygen-tolerant polymerization with an extremely low catalyst loading (50 ppb). This system demonstrated a broad applicability to various monomers, achieving successful polymerization of methacrylates, acrylates, and styrene. Additionally, efficient photo-ATRP on a large scale (250 mL) was achieved, resulting in narrow molecular weight polymers with high monomer conversions and high chain-end fidelity. This work provides an in-depth investigation into the regulatory process of photo-ATRP, offering new insights into the intricate mechanism of oxygen tolerance.展开更多
基金financially supported by the National Natural Science Foundation of China (No. 22271044).
文摘Organocatalyzed atom transfer radical polymerization(O-ATRP)is a pivotal technique for the synthesis of polymers with well-defined structures that are devoid of metallic residues.A major challenge in this area is the reduction of catalyst loading while maintaining precise control over polymer architecture and properties.Herein,we systematically evaluate the efficacy of six pyrazino[2,3-f][1,10]phenanthroline(pyzPhen)-based photoredox catalysts in photoinduced O-ATRP.Experimental results indicate that the introduction of various substituents markedly influences the photophysical properties and redox behavior of the catalysts,thereby resulting in differing catalytic efficiencies in the O-ATRP of methyl methacrylate(MMA).Following additional optimization,two highly efficient O-ATRP photocatalysts capable of exhibiting thermally activated delayed fluorescence(TADF)were successfully identified.Under visible light irradiation,TADF catalysts effectively mediated the controlled polymerization of MMA at a low loading level of 50 ppm,particularly when used in conjunction with the initiator DBMM.The catalytic systems demonstrate excellent temporal control,broad monomer applicability,and favorable compatibility with various initiators and solvent systems.This work offers new insights into the development of efficient,low-catalyst-loading,metal-free ATRP systems.
基金supported by the National Natural Science Foundation of China(22471054,22202056)Central Government Guided Local Science and Technology Development Fund Project(246Z2408G)Interdisciplinary Research Program of Natural Science of Hebei University(DXK202203).
文摘Development of highly efficient organic photocatalysts(OPCs)is imperative in the advancement of photoinduced atom transfer radical polymerization(photoATRP).Herein,we reported a class of OPCs consisting of(difluoro)quinoxaline acceptor units,and diphenylamine donor unit.Ultrafast femtosecond transient absorption(fs-TA)spectroscopy revealed that the photoexcited OPCs formed charge-transfer triplet(3CT)states via intersystem crossing.Well-controlled photoATRP was developed by using sub-ppm(parts per million molar ratio relatives to monomer)level of these OPCs.Furthermore,the photoATRP in sealed vials were tolerant towards a substantial amount of molecular oxygen,exhibiting accelerated polymerization rate after an inhibition period.Mechanistic study elucidated that two kinds of reactive oxygen species,superoxide(O_(2)^(−))_(3)and singlet oxygen(1O_(2)),were concurrently generated by photoinduced electron transfer and energy transfer,respectively,from the 3CT state of OPCs.The oxygen in the reaction system was consumed via the reaction of oxidize solvent by 1O_(2).
基金financial support of the National Natural Science Foundation of China(No.22271044).
文摘Substantial progress has been made over recent years in visible light-driven dual photoredox/copper catalyzed atom transfer radical polymerization (photo-ATRP) through the design of photocatalysts (PCs) and the optimization of reaction conditions. However, it remains challenging to achieve efficient photo-ATRP with low loadings of both photocatalyst and copper(II). In this study, two donor-acceptor organic PCs based on pyrazino[2,3-f][1,10]phenanthroline were successfully used to achieve efficient Cu(II)-mediated photo-ATRP. These organic PCs exhibit excellent visible light absorption capabilities and thermally activated delayed fluorescence (TADF) properties. Under blue light irradiation, the PCs facilitated highly efficient and oxygen-tolerant polymerization with an extremely low catalyst loading (50 ppb). This system demonstrated a broad applicability to various monomers, achieving successful polymerization of methacrylates, acrylates, and styrene. Additionally, efficient photo-ATRP on a large scale (250 mL) was achieved, resulting in narrow molecular weight polymers with high monomer conversions and high chain-end fidelity. This work provides an in-depth investigation into the regulatory process of photo-ATRP, offering new insights into the intricate mechanism of oxygen tolerance.
