A series of random copolymers of acrylamide and N-vinylimidazole, poly(AAm-co-NVI), with various compositions were prepared using redox copolymerization. The influence of environmental conditions such as pH, temperature, and ionic strength on the swelling behavior of the copolymeric hydrogels was investigated. The hydrogels exhibited the highest equilibrium swelling in basic medium at high temperature. Equilibrium swelling decreased with rising ionic strength at pH 5.0. As pH increased, equilibrium swelling of the hydrogels increased at pH 11.0 and I = 0.20 M. Swelling kinetics of the hydrogels was found to be non-Fickian at 25 degrees C. The process tended to be Fickian at higher pH and temperature. (c) 2005 Wiley Periodicals, Inc.