Synthesis Of Nanocomposite Hydrogels Research Articles

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

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.

Nanocomposite hydrogel consisting of Na‐montmorillonite with enhanced mechanical properties

ABSTRACTA new kind of nanocomposite (NC) hydrogel with Na‐montmorillonite (MMT) is presented in this article. The NC hydrogels were synthesized by free radical copolymerization of acrylamide and (3‐acrylamidopropyl) trimethylammonium chloride (ATC) in the presence of MMT and N,N′‐methylene‐bis‐acrylamide used as chemical cross‐linker. Due to the cation‐exchange reaction between MMT and ATC (cationic monomer) during the synthesis of NC hydrogels, MMT platelets were considered chemical “plane” cross‐linkers, different from “point” cross‐linkers. With increasing amount of MMT, the crosslinking degree enhanced, causing a decrease of the swelling degree at equilibrium. Investigations of mechanical properties indicated that NC hydrogels exhibited enhanced strength and toughness, which resulted from chemical interaction between exfoliated MMT platelets and polymer chains in hydrogels. Dynamic shear measurements showed that both storage modulus and loss modulus increased with increasing MMT content. The idea described here provided a new route to prepare hydrogels with high mechanical properties by using alternative natural Na‐MMT. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2015, 53, 1020–1026