Cationic ring-opening polymerization of 2-oxazolines and 2-oxazines in biomass-derived solvents

Abstract

In this study, we investigate the cationic ring-opening polymerization (CROP) of 2-oxazolines and 2-oxazines in two biomass-derived solvents, namely isosorbide dimethyl ether (DMI) and dihydrolevoglucosenone (Cyrene), environmentally friendly alternatives to conventional, fossil-based solvents such as acetonitrile and chlorobenzene. DMI matched the CROP kinetics and control of acetonitrile, with the advantage of being a non-toxic and biodegradable solvent. Furthermore, the living character of the polymerization process in DMI enabled us to synthesize well-defined, low-dispersity polymers with precise length and chain-end functionality. Furthermore, the potential of DMI is showcased by the successful synthesis of a triblock copolymer comprising three different monomers, as well as poly(2-ethyl-2-oxazoline) with a wide range of chain lengths. In turn, the polymerization rates were faster in Cyrene, but its application is limited by potential chain transfer reactions. Overall, this study may help to evaluate greener solvents and methods for polymer production, thereby mitigating the environmental impact of the increasing demand for polymer materials.