Swelling behavior of acrylic acid hydrogels prepared by γ-radiation crosslinking of polyacrylic acid in aqueous solution

Swelling behavior of anionic acrylic acid polyelectrolyte hydrogel synthesized by γ-radiation crosslinking of polyacrylic acid in aqueous solution was investigated. Cross-linked polyacrylic acid (PAA) hydrogel was synthesized using a two-step method. First, uncrosslinked PAA was synthesized by free-radical precipitation polymerization of acrylic acid in benzene. In the second step, PAA was dissolved in aqueous solution, and it was crosslinked with γ-irradiation. The swelling behavior of the gels was studied as a function of the concentration of PAA in aqueous solution during γ-irradiation, radiation dose, and pH of the swelling medium. In a buffered solution of pH 4, the degree of swelling ranged from 30 to 300 for irradiation doses ranging from 5 to 25 kGy, and the swelling was Fickian. On the other hand, in a buffered solution of pH 7 the degree of swelling ranged from 80 to 500 depending on the irradiation dose and the swelling was non-Fickian.