Dual pH- and Temperature-Responsive Hydrogels with Extraordinary Swelling/Deswelling Behavior and Enhanced Mechanical Performances

pH- and temperature-responsive semi-interpenetrating nanocomposite hydrogels (NC hydrogels) were prepared with surface-functionalized graphene oxide (GO) as the crosslinker, N-isopropylacrylamide (NIPAM) as the monomer, and chitosan (CS) as an additive. The effects of 3-(trimethoxysilyl)propylmethacrylate-modified GO sheets and CS content on various physical properties were investigated. Results show that PNIPAM/CS/GO hydrogels undergo a large volumetric change in response to temperature. Swelling ratios of PNIPAM/CS/GO hydrogels are much larger than those of the conventional organically crosslinked PNIPAM hydrogels. The deswelling test indicates that the deswelling rate was greatly enhanced by incorporating CS into the hydrogel network and using the surface-functionalized GO as the crosslinker. The pH-sensitivity of PNIPAM/CS/GO hydrogels is evident below their volume phase transition temperature. Moreover, the PNIPAM/CS/GO hydrogels have a much better mechanical property compared with traditional hydrogels even in a high water content of 90%. (c) 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015, 132, 41530.