Living anionic polymerization of 2-isopropenyl-2-oxazoline in continuous flow: From efficient synthesis to hydroxyl end-functionalized polymers

Abstract

Compared to conventional batch systems, flow reactors reduce the overall experimental effort for living polymerizations. Excellent heat transfer efficiency allows to safely perform exothermic reactions like anionic polymerizations in polar solvents at room temperature. By adjusting the flow rates during the reaction, a large number of samples with different molar masses can be obtained using the same setup. Herein the living anionic polymerization of 2-isopropenyl-2-oxazoline in a continuous flow system is reported, using a microstructured continuous flow reactor. Employing two different micromixers, poly(2-isopropenyl-2-oxazoline) (PiPOx) with molecular weights between 3000 g/mol (Р= 1.20) and 18,800 g/mol (Р= 1.9) was synthesized. The structure of the obtained polymers was confirmed by ¹H NMR spectroscopy and size exclusion chromatography. Additionally, end-capping experiments were performed with butylene oxide and ethylene oxide to introduce a terminal hydroxyl functionality. Successful functionalization was confirmed by ¹H NMR spectroscopy, and MALDI-TOF-MS. The present study not only reports an efficient method for preparing PiPOx, but also provides access to complex macromolecular architectures based on functional PiPOx, which were unattainable before by post-polymerization modification reactions such as macromonomers and comb polymers.