Three Birds with One Stone: AMT-Embedded PCL Microspheres Synergize with MXene to Achieve Triple-Healing Multifunctional Anticorrosion Coatings under Photothermal Conversion

In this paper, a multifunctional intelligent self-healing anticorrosion coating with the ability to realize triple healing in photothermal response as well as pH response was prepared. The composite coating matrix was shape memory polymer (SMP), and the filler was composed of PCL (polycaprolactone) microspheres that encapsulated the corrosion inhibitor AMT (2-amino-5-mercapto-1,3,4-thiadiazole), which was then loaded with MXene (Ti₃C₂T_<i>x</i>). Under light exposure, the PTM (PCL@AMT@MXene) composite microspheres achieved a photothermal effect; the temperature increase triggers the shape memory effect of SMP to achieve healing, and the PTM composite microspheres melted to further fill the scratches. In addition, the melting of PTM composite microspheres released the corrosion inhibitor AMT to further protect the metal. Moreover, during the corrosion protection process, the change of pH could also realize the release of corrosion inhibitor to protect the metal. The composite coating containing 10 wt % PTM demonstrated superior self-healing and corrosion resistance. Electrochemical impedance spectroscopy (EIS) measurements indicated that the |<i>Z</i>_{|<i>f</i>=0.01 Hz} for the PTM-10/SMP coating achieved a remarkable value of 1.96 × 10⁹ Ω·cm² after 40 days spent in a 3.5 wt % NaCl solution. This figure is four magnitudes higher than that observed for the pure SMP coating, resulting in an anticorrosion efficiency of up to 99.99%. The good photothermal conversion of the PTM-10/SMP coating could also effectively realize the resistance to ice as well as water droplet evaporation. The triple photothermal effect of self-healing, as well as the environmental response of the "gatekeeper", greatly improved the corrosion resistance of the metal.