Nanocomposite hydrogel consisting of Na-montmorillonite with enhanced mechanical properties

A 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. (c) 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2015, 53, 1020-1026