Superabsorbent polymeric materials VIII: Swelling behavior of crosslinked poly[sodium acrylate-co-trimethyl methacryloyloxyethyl ammonium iodide] in aqueous salt solutions

A series of xerogels based on sodium acrylate (SA), cationic comonomer, trimethyl methacryloyloxyethyl ammonium iodide (TMMAI), and N,N-methylene-bis-acrylamide (NMBA) were prepared by inverse suspension polymerization. The water absorbency and the swelling behavior for these high absorbent polymers in deionized water and various saline solutions were investigated. Results indicated that the water absorbency for the present copolymer gel increased when a small amount of TMMAI monomer was introduced into the SA gel, then decreased with increase in TMMAI content. The water absorbency was 583 g H2O/g for a gel sample in deionized water containing 2.5 × 10−3 molar fraction TMMAI. But a contrary result was observed for initial absorption rate, that is, the initial absorption rates increased with an increase of TMMAI in deionized water and 0.9 wt % NaCl solution. The absorbency in the chloride salt solution decreased with an increase in the ionic strength of the salt solution. Finally, the adsorption of copper ion by these gels was also investigated.