Thermosensitive hydrogels synthesized by fast Diels–Alder reaction in water

Novel thermosensitive hydrogels have been synthesized by aqueous Diels–Alder reaction of poly(N,N-dimethylacrylamide-co-furfuryl methacrylate) and N-[4-(formyl polyethylene glycol ester) bismaleimide. The gelation time was measured by a vial inversion method and the swelling behavior of dried hydrogel was studied by a general gravimetric method. It was found that water can accelerate Diels–Alder reaction while DMF can accelerate retro-Diels–Alder reaction. The gelation time decreases with the increase of temperature. Swelling/shrinking kinetics indicates that the as-prepared hydrogels have high swelling ratio and can respond to temperature. The strategy described here provides several advantages for the hydrogel formation including mild reaction conditions, no initiator or catalyzer, no organic solvent, tunable gelation rate, and thermal reversibility.