Near-infrared light-responsive hydrogels via peroxide-decorating MXene-initiated polymerization

Two-dimensional MXene Ti3C2Tx nanosheets with peroxide decorating (p-Ti3C2TX) are synthesized by a sonication-assisted MILD etching method. The obtained MXene can generate hydroxyl radical species, and act as an initiator for free-radical polymerization of a series of acrylic monomers without the use of light illumination or co-initiators. The monomers validated include acrylamide, N-isopropylacrylamide (NIPAM), N,N-dimethylacrylamide, methyl methacrylate, and hydroxyethyl methacrylate. By simply mixing N-isopropylacrylamide monomer and p-Ti3C2Tx nanosheets in deoxygenated condition, PNIPAM-based nanocomposite hydrogels are synthesized at high concentration of monomer. The nanocomposite hydrogels have a photothermal conversion efficiency of 34.7% and photothermal stability superior to pristine Ti3C2Tx. Taking advantage of the thermal responsive behavior of PNIPAM, the nanocomposite hydrogels are successfully exploited as remotely near-infrared light controlled “smart” window, fluidic valve and photodetectors.