Corbin Daniel A, McCarthy Blaine G, van de Lindt Zach, Miyake Garret M
Department of Chemistry, Colorado State University, Fort Collins, Colorado 80523-1872, United States.
Macromolecules. 2021 May 25;54(10):4726-4738. doi: 10.1021/acs.macromol.1c00640. Epub 2021 Mar 23.
Radical cations of photoredox catalysts used in organocatalyzed atom transfer radical polymerization (O-ATRP) have been synthesized and investigated to gain insight into deactivation in O-ATRP. The stability and reactivity of these compounds were studied in two solvents, ,-dimethylacetamide and ethyl acetate, to identify possible side reactions in O-ATRP and to investigate the ability of these radical cations to deactivate alkyl radicals. A number of other factors that could influence deactivation in O-ATRP were also probed, such as ion pairing with the radical cations, radical cation oxidation potential, and halide oxidation potential. Ultimately, these studies enabled radical cations to be employed as reagents during O-ATRP to demonstrate improvements in polymerization control with increasing radical cation concentrations. In the polymerization of acrylates, this approach enabled superior molecular weight control, a decrease in polymer dispersity from 1.90 to 1.44, and an increase in initiator efficiency from 78 to 102%. This work highlights the importance of understanding the mechanism and side reactions of O-ATRP, as well as the importance of catalyst radical cations for successful O-ATRP.
已合成并研究了用于有机催化原子转移自由基聚合（O-ATRP）的光氧化还原催化剂的自由基阳离子，以深入了解O-ATRP中的失活过程。在两种溶剂N，N-二甲基乙酰胺和乙酸乙酯中研究了这些化合物的稳定性和反应活性，以确定O-ATRP中可能的副反应，并研究这些自由基阳离子使烷基自由基失活的能力。还探讨了许多其他可能影响O-ATRP失活的因素，例如与自由基阳离子的离子配对、自由基阳离子氧化电位和卤化物氧化电位。最终，这些研究使得自由基阳离子能够在O-ATRP过程中用作试剂，以证明随着自由基阳离子浓度的增加，聚合控制得到改善。在丙烯酸酯的聚合中，这种方法实现了优异的分子量控制，聚合物分散度从1.90降至1.44，引发剂效率从78%提高到102%。这项工作突出了理解O-ATRP的机理和副反应的重要性，以及催化剂自由基阳离子对成功进行O-ATRP的重要性。
