Exploring Use of an Orthogonal Crosslinker to Create Controlled Thermoresponsive Hydrogels from LCST Tunable Thermoresponsive Polymers

Herein, a novel approach to create macroscale lower critical solution temperature (LCST) thermoresponsive hydrogels in a controlled manner using living cationic polymerization and a subsequent radical reaction is presented. By using a crosslinker capable of orthogonal reactions, 4-(vinyloxy)butyl methacrylate (VBM), which contains both vinyl ether and methacrylate moieties that react via cationic polymerization and radical reactions respectively, tremendous control over both the synthesis of the polymer structure as well as the hydrogel structure and its macroscale size and shape, by a post-polymerization UV light initiated radical reaction, is achieved. A series of random copolymers with the orthogonal crosslinker VBM, and LCST thermoresponsive monomers, methoxy ethyl vinyl ether (MOVE) or ethoxy ethyl vinyl ether (EOVE) or both, are synthesized. Introduction of VBM, even in small quantities, causes significant decreases in the observed phase transition temperatures for these thermoresponsive polymers and enables tuning of these temperatures. The hydrogels created from these polymers also exhibit clear LCST behavior with phase transition temperatures that are generally higher than for their corresponding polymers and over a wider temperature range. The use of this orthogonal reaction approach allows for control and design over both the polymer structure as well as that of the hydrogel.