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Mechanically Mediated Atom Transfer Radical Polymerization: Exploring Its Potential at High Conversions

Zhou, Yin-Ning, Li, Jin-Jin, Ljubic, Darko, Luo, Zheng-Hong, Zhu, Shiping
Macromolecules 2018 v.51 no.17 pp. 6911-6921
dimethyl sulfoxide, electron transfer, molecular weight, nuclear magnetic resonance spectroscopy, oxygen, polymerization, polymers, solubility
A well-controlled atom transfer radicfal polymerization of methyl acrylate (MA) was realized by mechanical mediation (mechanoATRP) in dimethyl sulfoxide (DMSO, 50% v/v). High conversions of typically over 90% were achieved. The resulting polymers had well-controlled molecular weights and very low dispersities (Đ = 1.03–1.09). No polymerization of MA was observed under various conditions from bulk up to 33.3% DMSO (v/v) solution. It was found that adding an equivalent volume of DMSO with respect to MA activated the polymerization. This finding suggested that DMSO played a crucial role in the mechanoATRP of MA. DMSO not only improved the solubility of CuBr₂ complex but also facilitated an electron transfer process in the mechanical reduction of CuBr₂. For a proof of the concept, a DMSO analogue acrylate, 2-(methylsulfinyl)ethyl acrylate (MSEA), was also polymerized. In addition, the high chain-end functionality of the polymers collected at ∼95% conversion was confirmed by ¹H NMR, MALDI-ToF-MS, and in-situ chain extension experiments. The extended chain polymers were characterized and found to have predicted molecular weights and low dispersities (Đ = 1.06). Chain extension in the presence of residual oxygen still yielded a well-controlled molecular weight but a slightly higher dispersity of 1.11. This work provided an in-depth insight into the mechanoATRP and demonstrated its good potential in producing well-defined polymers at high conversions.