Multiarm Core Cross-Linked Star-Shaped Poly(2-oxazoline)s Using a Bisfunctional 2-Oxazoline Monomer

Abstract

Poly(2-oxazoline)s are an attractive class of polymers that have a potential for biomedical applications. However, synthetic approaches for the preparation of 2-oxazoline-based star-shaped polymers are quite limited and are usually based on either end-capping of a living chain with a multifunctional terminator or utilizing a multifunctional initiator. Up until now, the use of a bis-oxazoline monomer as a cross-linking agent for the synthesis of core cross-linked star shaped poly(2-oxazoline) polymers has not been reported. Herein, we have developed a new bis-oxazoline cross-linker via a fast and efficient thiol click reaction with no catalyst and purification required. Moreover, we have utilized this cross-linker to prepare well-controlled core cross-linked star polymers with poly(2-oxazoline) arms in a straightforward manner. Synthesized star-shaped polymers were characterized in detail using an advanced gel permeation chromatography technique and were found to have a range of arms from <10 to over 1000. Furthermore, the effect of the reaction concentration, amount of cross-linker, and arm length on star formation were analyzed and the stars’ potential for dihydroxyanthroquinone encapsulation was explored.