Iron-Based Electrochemically Mediated Atom Transfer Radical Polymerization with Tunable Catalytic Activity

An iron-based electrochemically mediated atom transfer radical polymerization (eATRP) system with tunable catalytic activity was developed by adjusting the supporting electrolyte formula. Kinetic behaviors of the systems using four typical supporting electrolytes (namely, TBABr, TBAPF(6), TBACl, and TBABF(4)) were investigated. The type of anions was found to significantly affect the polymerization kinetics. TBAPF(6) system proceeded with a considerable polymerization rate, whereas TBABr system showed better controllability. Importantly, the effect of supporting electrolyte on eATRP kinetics (mainly on ATRP equilibrium) was confirmed through kinetic modeling. Furthermore, the effect of catalyst loading using TBAPF(6) as supporting electrolyte was also studied, and the results showed an uncontrolled polymerization for catalyst loading lower than 500 ppm. When hybrid supporting electrolyte (TBAPF(6)/TBABr) was used to tune catalytic activity, the polymerization slows down and the dispersity decreases with the increase in TBABr ratio. Polymers with a narrow molecular weight distribution (dispersity index <1.5) were obtained using 100% TBABr under 100 ppm catalyst. Besides, experimental attempt to improve the controllability by adding halogen donors was made, whereas the halogen donors just prolonged the induction period and no improvement was achieved. As a whole, a deeper understanding of kinetic studies is obtained by these controlled trials. (C) 2017 American Institute of Chemical Engineers