Random copolymer networks(RCNs) and Interpenetrating Networks(IPNs) were prepared s model networks in an attempt to investigate the pH-dependent swelling begaviors depending on physical and chemical natures of gel networks. Although the ionization profiles of sulfonic groups in the gel networks played the major role In pH-dependent swelling behaviors, the changes in pH-dependent swilling behaviors caused by the structural difference between RCNs and IPNS was observed This might be attributed to the differences in the intermolecular interaction between sulfonic groups and gel networks.