Superabsorbent polymeric materials. VI. Effect of sulfobetaine structure on swelling behavior of crosslinked poly(sodium acrylate-co-sulfobetaines) in aqueous salt solutions

Abstract

A series of xerogels based on sodium acrylate (SA), N,N-dimethyl(acrylamidopropyl) ammonium propane sulfonate (DMAAPS) or dimethyl(methacryloyloxy ethyl) ammonium propane sulfonate (DMAPS), and N,N′-methylene bisacrylamide (NMBA) was prepared by inverse suspension polymerization. The water absorbencies or swelling kinetic behaviors for these xerogels in water or various saline solutions were investigated. The swelling behaviors of these absorbents were related to their chemical structures, their compositions, and the nature of external salt solutions. The water absorbencies of these two copolymeric gel series in deionized water or in various salt solutions would be improved effectively by copolymerizing SA with a small amount of zwitterionic monomer (DMAAPS or DMAPS). The water absorbency of the gel containing DMAPS is larger than that of the gel containing DMAAPS when the amount of zwitterionic monomer in the copolymeric gel is 0.8 mol %. The tendency of the absorbency for these gels in dilute solution is in the order Cu2+ > Zn2+ > Co2+ > Ni2+ for CuCl2, ZnCl2, CoCl2, and NiCl2 aqueous solution, respectively. The absorbency and initial absorption rate for those gels are related with gel compositions and salt concentrations. Finally, the adsorption of cupric ion by these gels is also investigated. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 72: 1221–1232, 1999