Two-step synthesis of polyacrylamide/polyacrylate interpenetrating network hydrogels and its swelling/deswelling properties

A two-step polymerization technique is introduced to synthesize polyacrylamide/polyacrylate interpenetrating network (PAM/PAC IPN) hydrogels. The swelling ratio of the IPN hydrogel increases with the increase of the PAC content in PAM/PAC, and is smaller than the traditional PAM or PAC superabsorbents. A non-Fickian mechanism is observed in the swelling process, and the swelling changes from non-Fickian mechanism to Fickian mechanism with the increase of polyacrylate dosage in the hydrogel. The IPN hydrogel has typical pH-sensitivity and on–off effect. The deswelling properties and methyl orange dye removal are carried out based on the chelation of the carboxylic/carboxylate groups on the hydrogels with multivalent cations in solution. The hydrogel is expected to be used in the removal of heavy metal ions and dyes.