Abstract
A series of strong polyelectrolyte hydrogels was prepared from the sodium salt of 2-acrylamido-2-methylpropane sulfonic acid (AMPS) as the monomer and N,N 0 -methylene(bis)acrylamide (BAAm) as a crosslinker in aqueous solutions. The gel preparation temperature (Tprep) was varied between K22 and 25 8C. It was found that the swelling properties and the elastic behavior of the hydrogels drastically change at TprepZK8 8C. The hydrogels prepared below K8 8C exhibit a discontinuous morphology consisting of polyhedral pores of sizes 30–50 mm, while those formed at higher temperatures have a non-porous structure. The pore size of the networks increased by decreasing the charge density of the hydrogels, while addition of low molecular weight salts into the gelation system reduced the size of the pores. Calculations based on the equilibrium between the ice and unfrozen gel phases in the reaction system at low temperatures explain the results of observations. It was also shown that the hydrogels formed below K8 8C exhibit superfast swelling properties as well as reversible swelling– deswelling cycles in water and acetone. q 2005 Elsevier Ltd. All rights reserved.
Published Version
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