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

A series of xerogels based on sodium acrylate (SA), N,N-dimethyl(acrylamido propyl) ammonium propane sulfonate (DMAAPS) or dimethyl(methacryloyloxy eth yl) ammonium propane sulfonate (DMAPS), and N,N'-methylene bisacrylamide (N MBA) was prepared by inverse suspension polymerization. The water absorbenc ies or swelling kinetic behaviors for these xerogels in water or various sa line solutions were investigated. The swelling behaviors of these absorbent s were related to their chemical structures, their compositions, and the na ture of external salt solutions. The water absorbencies of these two copoly meric gel series in deionized water or in various salt solutions would be i mproved effectively by copolymerizing SA with a small amount of zwitterioni c monomer (DMAAPS or DMAPS). The water absorbency of the gel containing DMA PS is larger than that of the gel containing DMAAPS when the amount of zwit terionic monomer in the copolymeric gel is <0.8 mol %, but a contrary resul t is observed when the zwitterionic monomer content is >0.8 mol %. The tend ency of the absorbency for these gels in dilute solution is in the order Cu 2+ > Zn2+ > Co2+ > Ni2+ for CuCl2, ZnCl2, CoCl2, and NiCl2, aqueous solutio n, respectively. The absorbency and initial absorption rate for those gels are related with gel compositions and salt concentrations. Finally, the ads orption of cupric ion by these gels is also investigated. (C) 1999 John Wil ey & Sons, Inc.