Greener solvent systems for copper wire-mediated living radical polymerisation

Abstract

Copper wire-mediated living radical polymerisation (LRP) is a powerful tool that provides numerous opportunities for the development of new materials. It requires very low catalyst loading and mild reaction conditions; however, it typically involves the use of organic solvents. The authors have investigated the use of greener solvent systems to replace traditional volatile organic solvents without detrimentally affecting polymerisation. The effects of these alternative solvents on the control over polymerisation and polymer characteristics were investigated for the polymerisation of methyl acrylate initiated by ethyl 2-bromoisobutyrate. Copper wire-mediated LRP was conducted in dimethyl sulfoxide (DMSO), polyethylene glycol (PEG) and polypropylene glycol (PPG) and binary mixtures of PEG–DMSO, PEG–ethanol, PPG–DMSO and PPG–ethanol with total solvent volume fractions of 33 and 50%. Secondary solvent fractions in the binary mixtures were examined at 10 and 25% of the total solvent volume. The two most effective greener solvent systems were 33% v/v of 75% PEG–25% ethanol and 33% v/v of 75% PPG–25% ethanol. Both were shown to provide excellent control over polymerisation and a high degree of livingness. The poly(methyl acrylate) produced in these solvent systems retained high bromine chain-end functionality (>90%) and low dispersity (∼1·1).