Uses of electron‐beam irradiation to prepare pH‐ and temperature‐sensitive hydrogels from reactive poly(vinyl alcohol) grafts

Thermosensitive poly(vinyl alcohol)‐graft‐(maleic anhydride), PVA‐MA, and poly(vinyl alcohol)‐graft‐( N ‐isopropylacrylamide maleic anhydride) (PVA‐MA‐NIPAAm) copolymers containing carboxyl groups were prepared using electron beam irradiation at dose 80 kGy. The swelling ratios of the cross‐linked gels were measured at various temperatures. The LCST values were measured using DSC technique. The temperature dependence of the swelling ratios of the cross‐linked copolymers and terpolymers were measured at different temperatures. The swelling ratios of copolymers increased with increasing temperature up to 25–38°C, then decreased. The swelling behavior of both copolymers and terpolymers was referred to formation of hydrogen bonds between amide group of NIPAAm moieties and carboxyl group in MA moieties and to hydrophobic interaction due to methyl groups of NIPAAm. The swelling behaviors of these gels were analyzed in buffer solution at various pH. Swelling ratios of all gels were relatively high and they showed reasonable sensitive to pH.