New pH and temperature-sensitive hydrogels have been synthesized throug h copolymerization of anionic acrylate polyurethane prepolymer (P(U)) and N -isopropyl acrylamide (NIPAAm) under various feed ratios.Single glass transitio n t emperature was noticed from the DSC curves of the dried hydrogels,indicating of good miscibility between the two components.The pH sensitivity was much affecte d by the composition of the hydrogels and a lowest swelling degree was shown in hydrogel H4 with P(U)/NIPAAm feed ratio of 1/1.Hydrogel H4 also possessed low er critical solution temperature (LCST) of about 27℃ at both pH11 and pH7 sol utions.In the equilibrium hydrogel,most of the absorbed water was freezable wa ter with its content little affected by the hydrogel composition.Furthermore,t he gel strength was improved with incorporating more P(U) chains into the hydrog el.
A series of urethane acrylate anionomers(PU) in molar ratio of n (PEG)∶ n (DMPA)∶ n (HMDI)∶ n (2 HPA)= 0 3∶0 7∶(1 2～1 5)∶(0 44～1 1) were prepared in 3 steps. The structure of the prepolymer was confirmed by FT IR and 1 H NMR analysis. pH sensitive cross linked films were then obtained by UV polymerization of UAA. The swelling property of the films with respect to pH was much affected by the composition of the prepolymer. The film could swell and deswell rapidly and reversibly in buffer solutions of pH=3 and pH=11.
