Synthesis of acrylic acid hydrogel by γ-irradiation cross-linking of polyacrylic acid in aqueous solution

Polyacrylic acid (PAA) hydrogels are used extensively as a matrix in gastro-intestinal drug delivery systems. In this research, cross-linked PAA hydrogel was synthesized using a two step method. First. uncross-linked 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 cross-linked with gamma-irradiation. The swelling behaviour of the gels was studied in pH 4 and 7 to simulate gastric and enteric pH, respectively. In buffered pH 4 solution, the degree of swelling ranged from 30 to 300 for irradiation doses of 5 to 25 kGy and swelling was Fickian. On the other hand, in buffered pH 7 solution, the degree of swelling ranged from 80 to 500 depending on the irradiation dose and swelling was non-Fickian.