Thermo and pH dual responsive Poly (N-isopropylacrylamide-co-itaconic acid) hydrogels prepared in aqueous NaCl solutions and their characterization

In the present study, a simple but effective strategy was introduced to synthesize pH and thermo double responsive poly(N-isopropylacrylamide-co-itaconic acid) P(NIPAAm-co-IA) hydrogels with improved properties through preparation in aqueous sodium chloride solutions. With the increase of concentration of NaCl, the phase separations of the gels became more and more pronounced, thus induced different chain conformations and network structures. The equilibrium swelling ratios and deswelling/reswelling kinetics of the hydrogels were investigated under conditions of different pH, temperature and ionic strength. The result showed these hydrogels were able to absorb large amounts of water and exhibit improved temperature and pH sensitivities, which may be ascribed to the formed porous network structures. Their chemical structures, lower critical solution temperatures (LCSTs) and surface morphologies were also checked by Fourier transform infrared spectroscopy (FTIR), Differential scanning calorimetry (DSC) and scanning electron microscopy (SEM).