Near-Infrared Light-Responsive Poly(N-isopropylacrylamide)/Graphene Oxide Nanocomposite Hydrogels with High Elasticity

Novel near-infrared light-responsive poly(N-isopropylacrylamide)/graphene oxide (PNIPAM-GO) nanocomposite hydrogels with high elasticity have been successfully developed. The combination of graphene oxide (GO) and temperature-responsive poly(N-isopropylacrylamide) (PNIPAM) materials provides the hydrogels with near-infrared light-responsive property, because the GO materials could effectively generate photo-thermal heat due to their high optical absorbance in the near-infrared region. The high elasticity property of the PNIPAM-GO nanocomposite hydrogels is achieved by using very low concentration of N,N'-methylenebisacrylamide molecules as chemical cross-linkers and GO nano-sheets as physical cross-linkers. The low concentration of chemical cross-linker results in flexible polymer chains and GO nano-sheets toughen the hydrogels by hydrogen bond connection. Moreover, the GO nano-sheets in the hydrogel networks could dissipate the energy, making the hydrogels extremely stretchable. Because near-infrared light is a particularly attractive stimulus with easily adjustable intensity and wavelength perfectly used for remote controlling, the proposed PNIPAM-GO nanocomposite hydrogels with high elasticity are highly promising material candidates for responsive valves, actuators, artificial muscles, and so on.