Poly(2-oxazoline)-based core crosslinked star polymers via a combined cationic ring opening polymerization and click chemistry approach

Abstract

This study reports the synthesis of core crosslinked star-shaped poly(2-oxazoline)s (CC-sPOxs) via an “arm first” approach combining cationic ring opening polymerization (CROP) with a thiol–ene click reaction. The resulting polymers consist of hydrophilic poly(2-ethyl-2-oxazoline) (PEtOx) arms and a poly(2-(3-butenyl)-2-oxazoline) (PButEnOx) core. First, a series of linear block copolymers PEtOx-b-PButEnOx was synthesized by CROP. These copolymers were subsequently crosslinked through a thiol–ene reaction using the crosslinker 2,2′-(ethylenedioxy)diethanethiol, yielding CC-sPOxs. To optimize the formation of star-shaped polymers, the thiol–ene reaction was carried out with varying amounts of the crosslinking agent and different amounts of comonomers. The resulting polymers were characterized in terms of their molar mass, composition, and solution behaviour and their cytotoxicity was assessed, confirming their potential suitability in biology and medicine. A novel method for synthesizing non-toxic poly(2-oxazoline)s with a non-linear macromolecular topology, with a precisely defined molar mass and number of arms, is presented in this work.