Click chemistry for in situ formation of thermoresponsive P(NIPAAm-co-HEMA)-based hydrogels

The strategy for in situ chemical gelation of poly(N-isopropylacrylamide-co-hydroxylethyl methacrylate) [P(NIPAAm-co-HEMA)]-based polymers was demonstrated. Two types of new P(NIPAAm-co-HEMA) derivatives with alkyne and azide pendant groups, respectively, were prepared. When the solutions of the two derivatives were mixed together, a crosslinking reaction, a type of Huisgen's 1,3-dipolar azide-alkyne cycloaddition, in the presence of Cu(I) catalyst occurs. The morphology, equilibrium swelling ratio, swelling kinetics, and temperature response kinetics of the in situ gelated hydrogels were studied. In comparison with the conventional PNIPAAm hydrogel, because of the spatial hindrance of polymeric chains, the resulted hydrogels had a macroporous structure as well as a fast shrinking rate. The strategy described here presents a potential alternative to the traditional synthesis techniques for the in situ formation of thermoresponsive hydrogels. (c) 2008 Wiley Periodicals, Inc.