Electrochemically Mediated Atom Transfer Radical Polymerization of Methyl Methacrylate: The Importance of Catalytic Halogen Exchange

Electrochemically mediated atom transfer radical polymerization (eATRP) of methyl methacrylate (MMA) was studied in 1-butyl-3-methylimidazolium triflate ([BMIm][OTf]) and ethanol. When 2-bromopropionitrile and ethyl 2-bromoisobutyrate were used as initiators, poorly controlled or uncontrolled polymerizations yielding polymers with molecular weights largely exceeding the theoretical values were obtained. Poor control was attributed to a reactivity mismatch between initiator and dormant species, which was successfully suppressed by combining eATRP with catalytic halogen exchange. Well-defined polymers (Mn>30000 and Ð<1.2) were obtained in both solvents under optimized conditions. The possibility of using PMDETA as an inexpensive ligand in combination with ethyl α-bromophenylacetate as initiator was also successful. Good chain-end fidelity during eATRP was confirmed by chain extension of PMMA-Cl macroinitiator with MMA in ethanol.Polymers prepared in both solvents were found to be mainly syndiotactic, without any solvent effect on tacticity.