Versatile Synthesis of End-Functionalized Thermosensitive Poly(2-isopropyl-2-oxazolines)

Abstract

The synthesis of several end-functionalized poly(2-isopropyl-2-oxazolines) (PiPrOx) has been achieved via cationic ring-opening polymerization of 2-isopropyl-2-oxazoline. Poly(2-isopropyl-2-oxazolines) bearing primary amino groups at one chain end (Me-PiPrOx-NH2, with Mn ranging from 3600 to 9700) were obtained by conversion of hydroxyl-terminated poly(2-isopropyl-2-oxazolines) (Me-PiPrOx-OH) via phthalimide activation of the hydroxyl groups and subsequent hydrazine treatment. Heterotelechelic PiPrOx carrying an α-acetal and an ω-hydroxyl group (acetal-PiPrOx-OH) were prepared via cationic ring-opening polymerization of 2-isopropyl-2-oxazoline initiated with 3,3-diethoxy-1-propyl tosylate. The polymerizations carried out under mild conditions (40−45 °C) for extended periods of time yielded polymers of well-controlled molecular weight (MW) and narrow molecular weight distribution (MWD). Analysis of the polymers by 1H and 13C NMR spectroscopy, ion-exchange HPLC, and MALDI−TOF mass measurements indicated tha...