NIR photoresponsive shape memory polyurethanes composite with self-healing and anti-corrosion properties

The self-healing ability of organic coatings is crucial for restoring protective functions and achieving long-lasting corrosion protection in the case of coating defects. This article prepares a shape memory-assisted self-healing polyurethane composite with the dual response of light and heat (SMPUx-Uy@CS). The shape memory performance of the material is controlled by adjusting the addition ratio of polyether glycol with different molecular weights. The introduction of reversible quadruple hydrogen bonds (UPy) further enhances the microphase separation of the system, endowing the material with excellent mechanical properties and self-healing ability. Carbon nanospheres (CS) are added to produce a photothermal conversion effect under near-infrared (NIR) irradiation. On the one hand, it can achieve precise repair, and on the other hand, it can improve corrosion resistance. When PTMG-1000:PTMG-250 = 4:1, SMPU3-U30@CS-0.5 with 30% UPy and 0.5 wt.% CS has the best comprehensive performance, with a tensile strength of 8.42 MPa and an elongation at a break of 194.91%. The surface scratches of the composite coating can be healed after 60 s under 3 W/cm2 NIR irradiation. Magnesium alloy with SMPU3-U30@CS-0.5 coating has a corrosion potential of −1.34 V and corrosion current density of 5.37 × 10−9 A cm−2, and the damaged coating recovers well in corrosion resistance after 300 s of NIR irradiation. Thanks to the maze effect and hydrophobic performance, the addition of CS is beneficial for improving the anti-corrosion performance of the coating. The experimental results indicate that the repair efficiency of NIR is much higher than that of thermal repair, making it more green, environmentally friendly, and sustainable. This article provides a straightforward, green synthesis strategy for constructing self-healing coatings with efficient corrosion resistance.