SYNOPSISA series of crosslinked poly(sodium acrylate-co-hydroxyethyl methacrylate) based on sodium acrylate (SA), 2-hydroxyethyl methacrylate (HEMA), and N,N-methylene-bis-acrylamide (NMBA) are prepared by inverse suspension polymerization. The resultant crosslinking polymers are xerogellants. This work investigates not only the absorbency or swelling behavior for these xerogellants composed of different ratios of HEMA/SA in water, but also the effects of various salts and p H values on the swelling properties. Experimental results indicate that the absorbency in deionized water decreases with an increase in the HEMA in copolymeric gel, which is related to the degree of expansion of the network and the strength of the hydrophilic group. The absorbency in the chloride salt solutions decreases with an increase in the salt concentration (swelling is 50 times for the IA group chloride salt solutions, but is less than 5 times for the IIA group salt solution), owing to the osmosis of water and ions between the polymeric gel and the external solution. A decrease in the extent of swelling occurs for divalent and trivalent chloride salt solutions. For the salt solutions of the same ionic strength, the swelling amount has the following tendency:LiCl(aq) = NaCl(aq) = KCl(aq), CaCl,(aq) < SrCl,(aq) < BaCl,(aq), and Fe3+ > Ca2+ > Zn2+ > Cu2+. These orders are related to the complexing ability between metallic cations and the carboxylate group in the polymeric chains. Finally, the adsorption of ferric ion by these gels is also investigated.

A series of xerogels based on sodium acrylate (SA), 3-dimethyl (methacryloyloxyethyl) ammonium propane sulfonate (DMAPS), and N,N-methylene-bis-acrylamide (NMBA) are prepared by inverse suspension polymerization. The water absorbencies or swelling behaviors for these xerogels in water or various saline solutions are investigated. Results obtained from this study show that the water absorbency respectively exhibit a value of 1435 g H 2 O/g sample and 96 g H 2 O/g sample in deionized water and 0.9 wt % NaCl solution at a gel containing 1.88 1 10 03 molar ratio of DMAPS while the extent of 1.53 1 10 03 molar ratio (0.25 wt % based on total monomer) of NMBA was used in the polymerization. The absorbency in the chloride salt solutions decreases with an increase in the ionic strength of salt. For the same ionic strength of various salt solutions, the swelling amount has the following tendency: Na / ú Fe 3/ ú Al 3/ ú Ca 2/ for the higher ionic strength of 5 1 10 03 -2 1 10 02 M and Na / ú Fe 3/ ú Ca 2/ ú Al 3/ for the lower ionic strength of õ 2 1 10 04 M. The bound water found by DSC investigation is approximately equal to 2 g H 2 O/g sample. The pH effect and thermal effect on the water absorbency for these xerogels are also investigated.