Near-infrared light-responsive hydrogels <i>via</i> peroxide-decorated MXene-initiated polymerization

Abstract

Two-dimensional MXene Ti₃C₂T _<i>x</i> nanosheets with peroxide decoration (p-Ti₃C₂T _<i>x</i> ) are synthesized by a sonication-assisted MILD etching method. The obtained MXenes 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 analyzed include acrylamide, <i>N</i>-isopropylacrylamide (NIPAM), <i>N</i>,<i>N</i>-dimethylacrylamide, methyl methacrylate, and hydroxyethyl methacrylate. By simply mixing <i>N</i>-isopropylacrylamide monomers and p-Ti₃C₂T _<i>x</i> nanosheets under deoxygenated conditions, PNIPAM-based nanocomposite hydrogels are synthesized using a high concentration of the monomer. The nanocomposite hydrogels have a photothermal conversion efficiency of 34.7% and photothermal stability superior to that of pristine Ti₃C₂T _<i>x</i> . Taking advantage of the thermal responsive behavior of PNIPAM, the nanocomposite hydrogels are successfully exploited as remotely near-infrared light controlled "smart" windows, fluidic valves and photodetectors.