Interplay between the Oxygen Reduction Reaction and Atom Transfer Radical Polymerization with Molecular Cu-Based Catalysts in Water

Abstract

Determining the relationships between the catalyst structures of Cu-based molecular complexes and their performances in the oxygen reduction reaction (ORR), hydrogen peroxide reduction reaction (HPRR), and electrochemically mediated Atom Transfer Radical Polymerization (eATRP) is crucial for advancing radical polymerization in aerobic environments. Hence, Cu/tris(2-pyridylmethyl) amine (TMPA) was compared with Cu catalysts with TMPA ligands containing electron-donating para-substituents for aqueous ORR/HPRR catalysis and ATRP. Para-substitution decreased the ORR and HPRR activities, thereby reducing the O₂ consumption compared to that of Cu/TMPA. Para-substituted TMPA catalysts were suitable for acrylate polymerization, with M_w/M_n < 1.3, whereas the reaction rates of methacrylates were too high, leading to polymethacrylates with high M_w/M_n. Our results show that ORR/HPRR and ATRP are competitive, intertwined processes in aerobic water, with reactivities diverging upon the introduction of electron-donating para-substituents. These findings will facilitate future efforts to optimize Cu-based molecular catalysts by tuning their ligand structures to improve the performance of both ATRP and ORR/HPRR.