Scale-up of microwave-assisted polymerizations in continuous-flow mode: Cationic ring-opening polymerization of 2-ethyl-2-oxazoline

Microwave-assisted polymerizations is a growing field of interest because the use of microwave irradiation instead of thermal heating was demonstrated to result in faster, cleaner, and higher yielding reactions. To overcome the one-at-a-time nature of preparing polymerizations in single microwave vials and the possible scale-up method for microwave-assisted polymerizations, the use of continuous-flow reactions under microwave irradiation seems to be ideal. In this contribution, we report for the first time the use of different continuous-flow microwave reactors for polymerizations, using the cationic ring-opening polymerizations of 2-ethyl-2-oxazoline as a model system. In addition, the observed broader molecular-weight distributions were correlated to residence time distributions of the continuous-flow reactors that were determined using methyl orange as the flow marker.