Poly(2-isopropenyl-2-oxazoline) as a versatile platform towards thermoresponsive copolymers

Abstract

The present study describes the synthesis of thermoresponsive polymers with tailorable properties using a simple, straightforward and robust polymer modification approach. Herein, we first report a simple strategy to obtain poly(2-isopropenyl-2-oxazoline) (PiPOx) polymers with narrow distribution by controlled living anionic polymerization initiated with commercially available n-butyllithium. Further on, the well-defined PiPOx polymer is reacted with four aliphatic acids by a partial ring-opening reaction of the pendant 2-oxazoline side chains, thus enabling access to a large structural diversity of statistical (co)polymers with LCST behavior. Depending on the final PiPOx copolymer composition and the hydrophobic character of the side-chain functionalities, the cloud point temperatures (T_CP) of the resulting PiPOx copolymers span the entire liquid water temperature scale (5 °C to 97 °C). As such, this work opens up the use of PiPOx as a highly versatile platform for advanced smart materials as the retained 2-oxazoline side chains can be further modified to introduce functionalities.