Preparation and swelling behavior of thermally cross-linked poly(vinyl alcohol) and poly(acrylic acid) hydrogel

The thermal cross-linking of poly(vinyl alcohol) (PVA) using poly(acrylic acid) (PAA) was conducted to prepare a PVA/PAA hydrogel, rather than using conventional methods including repetitive freezing and thawing cycles, and to form interpenetrating networks. The gelation content and water content were investigated in the samples of PVA and PAA having various molecular weights and PAA contents in the hydrogels. From the results of measuring the gelation content and water content we revealed that the cross-linking was complete between the two polymers and that the swelling behaviors depended on the mixing ratio and pH of the medium. The permeation of drugs was tested using Indomethacin as the model drug; it increased constantly with time. The permeation coefficient through the hydrogels was 4.25 × 10⁷ cm²/s.