Synthesis and characterization of hydrogels based on gamma irradiation of acrylic acid and methacrylic acid

Abstract In this work, hydrogels based on different ratios of acrylic acid (AAc) and methacrylic acid (MAc) monomers were prepared by gamma radiation copolymerization. The hydrogels were characterized by IR spectroscopy and thermogravimetric analysis (TGA). The effect of temperature and pH on the degree of swelling of AAc/MAc hydrogels was also studied. The results showed that the gel fraction of AAc is relatively higher than MAc, while the gel fraction of AAc/MAc hydrogels decreased slightly with increasing the ratio of MAc monomer in the initial solution. The IR spectroscopic analysis indicates the formation of copolymer networks and the presence of hydrogen bonding. The thermal study showed that PAAc hydrogel displayed higher thermal stability than PMAc and AAc/MAc hydrogels, over the studied compositions. The results showed that PAAc hydrogel reached equilibrium swelling state in water after 4 h, whereas PMAc and AAc/MAc hydrogels reached the equilibrium after 7 h. In this regard, AAc/MAc hydrogels showed degree of swelling in water lower than PAAc and higher than PMAc hydrogels. It was found that the swelling of the hydrogels based on AAc and MAc monomers or their copolymers increases with increasing temperature up to 50°C. Moreover, it was observed that the degree of swelling of hydrogels were not affected by increasing the pH values up to 4 and increased greatly within the pH values from 5 to 9. POLYM. COMPOS., 2009. © 2008 Society of Plastics Engineers