NIR light-induced functionalized MXene as a dynamic-crosslinker for reinforced polyurethane composites with shape memory and self-healing

Near infrared (NIR) light-driven shape memory can expand the potential of polyurethane as advanced materials. Herein, polyurethane composites (PU/B-THDI/FMXene) with Diels-Alder (D-A) reversible crosslinking feature were fabricated in combination with internal crosslinker bis(2-hydroxyethyl) terephthalate (BHET) modified hexamethylene-diisocyanate trimer (B-THDI), and functionalized MXene (FMXene). FMXene was prepared via 3-isocyanatopropyltriethoxysilane (IPTS) as a coupling agent between MXene and furfuryl alcohol (FA) through covalent bonds, thereby enabling dynamic crosslinking. FMXene can not only form D-A dynamic-crosslinked network with PU chain, but also retain excellent thermal conductivity. Only containing 2 wt% FMXene en-dows PU/B-THDI/FMXene2 composites with fast shape memory (<15 s, shape-fixity and recovery rates are 88.1 % and 97.8 %, respectively), self-healing (<100 s, the healing efficiency for tensile strength and elongation at break are 88.0 % and 91.0 %, respectively), good self-healing repeatability (79.1 %) and thermal conductivity (0.661 W m(-1) K-1). Moreover, PU/B-THDI/FMXene2 exhibits remarkable mechanical performances (tensile strength of 16.9 MPa and elongation at break of 233.9 %) and thermal stability. In addition, B-THDI with crosslinking and toughening effects provides certain strength and flexibility for PU. Thus, this work may open new approaches for developing photothermal-induced shape memory polyurethane.