Nanocomposite hydrogel of chitosan-g-poly acrylamide/ nanoclay: effect of degree of cross-linking on their swelling

Abstract

In this study a chitosan-g-Polyacrylamide hydrogel was prepared through graft copolymerization in the presence of an appropriate amount of potassium persulfate as the initiator and different ratio of methylene bis acrylamide as the crosslinker agent. After dewatering the gels in acetone and being dried in oven, the swelling behaviors of hydrogels in different media such as distilled water, NaCl 0.15M, basic buffer with pH=10 and acidic buffer with pH=3 were evaluated. The gel with the highest swelling degree (i.e. 1/60 crosslinker) was selected to be used in the synthesis of nanocomposite hydrogel. Nanocomposite hydrogels with 1, 3, 5 percent of nanoclay were synthesized respectively. Swelling behaviors of nanocomposite hydrogels were examined. The results of swelling test showed a decrease in the swelling extent as the crosslinker ratio is increased. The result showed that different swelling behaviors as the media of experiment is changed. They showed a lower swelling extent in saline media than in distilled water. The results of swelling test in buffer media show lower swelling extent than in distilled water and swelling extent in acidic buffer with pH=3 is greater than swelling extent in basic buffer with pH=10. The swelling extent of nanocomposite increases slightly with the increase of nanoclay content up to 1%. More increase in the nanoclay content caused a drastic decrease in the swelling extent as well.