Benchaphanthawee Wachara, Peng Chi-How
Department of Chemistry and Frontier Research Center on Fundamental and Applied Sciences of Matters, National Tsing Hua University, 101, Sec 2, Kuang-Fu Rd., 30013, Hsinchu, Taiwan.
Chem Rec. 2021 Dec;21(12):3628-3647. doi: 10.1002/tcr.202100122. Epub 2021 Jun 15.
Cobalt complexes have played an essential role in different chemical reactions. One of them that has attracted substantial attention in polymer science is cobalt mediated radical polymerization (CMRP), which is famous for its remarkable efficiency in controlling the radical polymerization of vinyl acetate (VAc) and other less active monomers (LAMs). Two pathways, reversible termination (RT) and degenerative transfer (DT), were recognized to control the polymerization in CMRP and could be further used to rationalize the mechanism of other RDRP methods. These control mechanisms were then found to be correlated to the redox potential of cobalt complexes and thus could be judged more quantitatively. The control of polymer composition and tacticity could also be achieved by using CMRP. The hybridization of CMRP and atom transfer radical polymerization (ATRP) could directly synthesize the vinyl acetate/methyl methacrylate and vinyl acetate/styrene block copolymers in one pot. The copolymer of acrylates and 1-octene could be obtained by visible-light-induced CMRP. With the addition of bulky Lewis acid, CMRP of N,N-dimethylacrylamide (DMA) showed high isotacticities with the contents of meso dyads (m) and meso triads (mm) up to 94 % and 87 %, respectively, and generated the crystalline PDMA with T as high as 276 °C. This personal account reviewed the development of CMRP with the mechanistic understanding, the control of composition and stereoselectivity of the polymeric products, and its perspective.
钴配合物在不同的化学反应中发挥了重要作用。其中在高分子科学领域备受关注的一种反应是钴介导的自由基聚合（CMRP），它以在控制醋酸乙烯酯（VAc）和其他活性较低单体（LAMs）的自由基聚合方面具有显著效率而闻名。人们认识到有两种途径，即可逆终止（RT）和退化转移（DT），来控制CMRP中的聚合反应，并且这两种途径可进一步用于阐释其他可逆失活自由基聚合（RDRP）方法的机理。随后发现这些控制机理与钴配合物的氧化还原电位相关，因此可以进行更定量的判断。通过使用CMRP还可以实现聚合物组成和立构规整性的控制。CMRP与原子转移自由基聚合（ATRP）的杂化可以在一锅法中直接合成醋酸乙烯酯/甲基丙烯酸甲酯和醋酸乙烯酯/苯乙烯嵌段共聚物。丙烯酸酯与1-辛烯的共聚物可以通过可见光诱导的CMRP获得。在加入大体积路易斯酸的情况下，N，N-二甲基丙烯酰胺（DMA）的CMRP显示出高全同立构规整性，内消旋二元组（m）和内消旋三元组（mm）的含量分别高达94%和87%，并生成了熔点高达276℃的结晶聚N，N-二甲基丙烯酰胺（PDMA）。本文综述了CMRP的发展，包括其机理认识、聚合物产物的组成和立体选择性控制及其前景。
