Synthesis and swelling behaviors of sodium carboxymethyl cellulose-g-poly(AA-co-AM-co-AMPS)/MMT superabsorbent hydrogel

Superabsorbents were synthesized by graft copolymerization of acrylic acid (AA)/acrylamide (AM)/2-acrylamido-2-methyl-1-propanesulfonic acid (AMPS) onto sodium carboxymethyl cellulose (CMC) and montmorillonite (MMT) by using potassium persulfate (KPS) as a free radical initiator, in the presence of N,N′-methylenebisacrylamide (MBA) as a crosslinking agent. The structure and morphologies of the superabsorbents were characterized by Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA) and scanning electron microscope (SEM). Superabsorbent comprised a porous crosslink structure of MMT and CMC with side chains that carry carboxylate, carboxamide and sulfate. The swelling behaviors of the superabsorbent were dependant on the pH of external solutions, particle size and the concentration of the salt solution. The effect of four cationic salt solutions on the swelling had the following order: K+ > Na+ > Ca2+ > Mg2+.