Investigations regarding the cationic ring-opening polymerization of 2-phenyl-2-oxazoline under microwave irradiation and conventional heating are reported. This study was inspired by contradictory reports of the (non-)-existence of non-thermal microwave effects that might accelerate the cationic ring-opening of 2-oxazolines. The polymerization of 2-phenyl-2-oxazoline was investigated under pressure in acetonitrile and under reflux (or at the boiling point of butyronitrile in a closed vessel) in butyronitrile utilizing a single-mode microwave reactor and automated synthesis robots with conventional heating.