Superabsorbent polymeric material. V. Synthesis and swelling behavior of sodium acrylate and sodium 2-acrylamido-2-methylpropanesulfonate copolymeric gels

Abstract

A series of xerogels based on sodium acrylate (SA), sodium 2-acrylamido-2-methyl propanesulfonate (NaAMPS), and N,N-methylene-bis-acrylamide (NMBA) are prepared by inverse suspension polymerization. The water absorbency and swelling behavior for these high absorbent polymers in deionized water and transition salt solutions are investigated. Experimental results indicated that the absorbency in deionized water increases with an increase of the NaAMPS content in the copolymeric gels, which is related to the degree of charge density of the network and the strength of hydrophilic group. The extent of crosslinking agent also influenced the swelling capacity because of elastic chain force of the polymer chain. The absorbency in chloride salt solutions decreases with an increase in the ionic strength of salt. But the decrease of absorbency is different in monovalent and multivalent salt solution. This behavior can be accounted for in terms of counterion condensation or screening effect for monovalent cations, as well as complexation for multivalent cations. The swelling rates in various salt solutions for these xerogels are also investigated. At last, SA-NaAMPS copolymeric gels were used for ion adsorption. But the result showed that the adsorptive amount of transition metal ions for SA-NaAMPS copolymeric gels was lower than that for pure poly(SA) gel. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 69: 229–237, 1998