Synthesis, characterization, and swelling behaviors of a pH-responsive CMC-g-poly(AA-co-AMPS) superabsorbent hydrogel

New superabsorbent hydrogels were synthesized through free radical graft copolymerization of partially neutralized acrylic acid (AA) and 2-acrylamido-2-methylpropanesulfonic acid (AMPS) onto carboxymethyl cellulose (CMC) backbones. The structure and morphology of the synthesized superabsorbent hydrogels were characterized by Fourier transform infrared spectroscopy and scanning electron microscope. The effect of the molar ratio of AMPS to AA, the APS concentration, and the CMC content on swelling ratio was optimized. The swelling properties in various pH solutions and saline solutions as well as the swelling kinetics were also evaluated. Results showed that the introduction of AMPS enhanced the swelling capacity, swelling rate, and salt-resistance of the superabsorbent hydrogels. Moreover, the hydrogels exhibited smart swelling behavior in multivalent salt solutions and better reversible pH sensitivity in the pH 2.0 and 7.0 solutions, which makes the hydrogels available as a candidate for drug delivery systems.