Preparation of alginate/poly(N-isopropylacrylamide) semi-interpenetrating and fully interpenetrating polymer network hydrogels with gamma-ray irradiation and their swelling behaviors

Abstract

Semi-interpenetrating polymer network (semi-IPN) and fully interpenetrating polymer network (full-IPN) hydrogels composed of alginate and poly(N-isopropylacrylamide) were prepared with gamma-ray irradiation. The semi-IPN hydrogels were prepared through the irradiation of a mixed solution composed of alginate and N-isopropylacrylamide (NIPAAm) monomer to simultaneously achieve the polymerization and self-crosslinking of NIPAAm. The full-IPN hydrogels were formed through the immersion of the semi-IPN film in a calcium-ion solution. The results for the swelling and deswelling behaviors showed that the swelling ratio of semi-IPN hydrogels was higher than that of full-IPN hydrogels. A semi-IPN hydrogel containing more alginate exhibited relatively rapid swelling and deswelling rates, whereas a full-IPN hydrogel showed an adverse tendency. All the hydrogels with NIPAAm exhibited a change in the swelling ratio around 30-40 degrees C, and full-IPN hydrogels showed more sensitive and reversible behavior than semi-IPN hydrogels under a step-wise stimulus. In addition, the swelling ratio of the hydrogels continuously increased with the pH values, and the swelling processes were proven to be repeatable with pH changes.