The supplemental activator reducing agent atom transfer radical polymerization (SARA ATRP) with catalytic system composed of Cu(0) and CuBr2/Me6TREN at room temperature using different sulfolane/co-solvent-based mixtures is reported. Three different co-solvents were studied: 1-butyl-3-methylimidazolium hexafluorophosphate (BMIM-PF6), water, and tetraethylene glycol (TEG). The results revealed a synergistic effect between sulfolane and BMIM-PF6, which enhanced the polymerization rate several times while maintaining a stringent control over the polymerization. The catalytic system was used as proof-of-concept for the SARA-ATRP of methyl methacrylate (MMA), styrene (Sty), and vinyl chloride (VC). The addition of 10% of water (or TEG) to the sulfolane/BMIM-PF6 mixture resulted in fast polymerization rates. The results presented in this manuscript highlight the importance of the sulfolane as an universal industrial solvent for SARA-ATRP of different monomer families. (C) 2017 Wiley Periodicals, Inc.