Synthesis and characterization of pH-responsive carboxymethyl chitosan-g-polyacrylic acid hydrogels

In this work, carboxymethyl chitosan-g-polyacrylic acid (CMC-g-PAA) hydrogel was synthesized by a free radical grafting cross-linking route. The structure of the CMC-g-PAA hydrogels was characterized by a Fourier transform infrared spectroscope (FTIR), and the morphologies were observed by scanning electron microscopy (SEM). The swelling kinetics investigations demonstrated that the equilibrium swelling (Qe) of the grafting network hydrogels depended on compositional ratios and pH of the buffer solutions. The equilibrium swelling values were increased with increasing the carboxymethyl chitosan contents and pH values, which was in agreement with maximum theoretical water contents fitted by swelling kinetic data. The chitosan-g-polyacrylic acid hydrogels comply with a non-Fickian for pH=1.4 and pH=7.0 of the buffer solutions. Therefore, the swelling behavior of the chitosan-g-polyacrylic acid hydrogels may be controlled and modulated by means of the compositional ratios of carboxymethyl chitosan to acrylic acid and pH of the buffer solutions.