A series of amphoteric, superabsorbent polymers [poly(acrylic acid-co-diallyldimethylammonium chloride)] with different molar ratios of anionic groups to cationic groups were prepared by solution polymerization to investigate their swelling behaviors and the controlled release of agrochemicals. Various factors, including the solution PH, the concentrations of different salt solutions, and the temperature, were studied. The dynamic parameters of hydrogels at different temperatures suggested that diffusion was Fickian at lower temperatures, whereas non-Fickian diffusion prevailed at higher temperatures. A copolymer hydrogel with a low anionic-group/cationic-group ratio showed a higher swelling capacity in water and higher salt tolerance. Also, the anionic-group/cationic-group ratio was not the dominant factor in determining the water retention. A poly(acrylic acid-co-diallyldimethylammonium chloride) hydrogel could control the release of agrochemicals effectively. (c) 2006 Wiley Periodicals, Inc.