Double-Network Hydrogel Consisting of Nano Na-Montmorillonite with Enhanced Mechanical and Antimicrobial Properties

(3-Acrylamidopropyl)trimethylammonium chloride (ATC), acrylamide and montmorillonite (MMT) without organic modification were synthesized through free radical polymerization to strengthen the mechanical properties of hydrogels. MMT platelets were considered as chemical "plane" cross-linkers different from "point" cross-linkers because of the cation-exchange reaction between MMT and ATC (cationic monomer) during the synthesis of hydrogels, while a double network was used to improve the mechanical properties of the hydrogels. Investigations of compressive and tensile properties indicated that compressive modulus and stress, fracture stress, ultimate strain and Young's modulus were significantly improved in the presence of MMT. The mechanical properties of double-network hydrogels improved with increasing monomer concentration of the first network. Scanning electron microscopy (SEM) revealed that large quantities of micro-network structures were located in the pores and the formation of embedded micro-network structures led to an increase in the compressive strength and toughness. Moreover, the gels with ATC exhibited good antibacterial effects against E. coli and S. aureus. These developments provide a new route to prepare hydrogels with high mechanical properties.