Preparation and determination of swelling behavior of poly(acrylamide-co-acrylic acid) hydrogels in water

Hydrogels with varying crosslinking densities were prepared from the acrylamide/acrylic acid and acrylamide/acrylic/poly(ethylene glycol) systems by the redox copolymerization method. Average molecular weights between crosslinks, percent swelling, swelling equilibrium values, and diffusion/swelling characteristics (i.e., the structure of network constant, the type of diffusion the initial swelling rate, diffusion coefficients, and swelling rate constant) were evaluated for both hydrogel systems. The prepared hydrogels have shown mass swelling capabilities in the range of 663–755% (for AAm/AA hydrogels) and 635–800% (for AAm/AA/PEG 4000 hydrogels). Water diffusion into hydrogels was found to be non-Fickian type diffusion. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 94: 1526–1531, 2004