Preparation and Swelling Properties of CrossLinked Poly(N-isopropylacrylamide)/(Sodium Alginate/Poly(N-isopropylacrylamide)) Semi-interpenetrating Polymer Network Hydrogel

Cross-linked poly(N-isopropylacrylamide)/sodium alginate/linear poly(N-isopropylacrylamide) semi-interpenetrating polymer network (Cr-PNIPAAm/(SA/PNIPAAm) semi-IPN) hydrogels were prepared by addition of sodium alginate and linear PNIPAAm into cross-linked PNIPAAm hydrogel network. Results indicate that the mass ratios of SA to linear PNIPAAm have little effects on the swelling ratios of Cr-PNIPAAm/(SA/PNIPAAm) semi-IPN hydrogels in weakly alkaline medium (pH=7.4). Whereas the swelling ratios of the hydrogels increase with the reduce of the mass ratios of SA to linear PNIPAAm in strong acidic medium (pH=1.0). Compared with PNIPAAm hydrogels, the deswelling rates of CrPNIPAAm/(SA/PNIPAAm) semiIPN hydrogels are greatly enhanced due to the concurrent effect of the linear PNIPAAm and hydrophilic SA.