Gamma radiation synthesis of comb-type graft hydrogels based on poly(acrylic acid) and 4-vinylpyridine

A pH-sensitive comb-type hydrogel was obtained by gamma radiation polymerization and crosslinking of acrylic acid (AAc) in solution. The pH-sensitive 4-vinylpyridine (4VP) was then grafted to the poly acrylic acid (PAAc) hydrogel using gamma radiation from a 60Co source. The comb type graft polymers obtained (net-PAAc)-g-4VP has been studied through determination of graft yield and swelling behavior. The critical pH value was found to be 5.6. The apparent mechanical properties appear to be qualitatively better than hydrogels of PAAc upon swelling. The new comb-type system presents faster swelling response (30 h) than the polyacrylic acid hydrogel (50 h). The increase in dose rate from 7.3 to 11.3 kGy h−1, increase the radiation grafting percentage of 4VP in the system. Comb-type polymers were also characterized by DSC, TGA and FTIR-ATR.