Functionalized chitosan microcapsules with pH-triggered release enable photothermal self-healing smart anti-corrosion coatings

Accordion MXene carriers produce MBT-loaded CS@M-T microcapsules; chitosan acts as pH-triggered responsive switch. • The MXene barrier, pH inhibition & photothermal healing enhance coating long-term anti-corrosion performance. • CS@M-T microcapsules in SMP offer coatings pH-responsive anti-corrosion and NIR photothermal self-healing capacities. • The pH-responsive CS@M-T microcapsules in SMP coatings prevent inhibitor leakage and scratch-induced failure. Organic anti-corrosion coatings have been widely utilized in the domain of metal corrosion protection. However, challenges such as the premature release of corrosion inhibitors during application and the inability of scratched coatings to self-heal have driven researchers to develop innovative corrosion-resistant protective coatings. This study presents a novel active anti-corrosion organic coating that exhibits pH-responsive and photothermal self-healing properties. To tackle these issues, accordion-shaped MXene (Ti 3 C 2 T x ), was synthesized to load 2-mercaptobenzothiazole (MBT), which was subsequently encapsulated with chitosan (CS) to create CS@M-T micro-nano capsules. These capsules were integrated into shape-memory polymers (SMP) for enhanced metal corrosion protection. The chitosan (CS) within the composite endows the capsules with pH-triggered release performance, effectively regulating the release of the corrosion inhibitor. Research findings indicate that under near-infrared light irradiation, the composite coating can achieve temperatures of 101°C，with a geometric self-healing rate for coating scratches of approximately 70%; after 30 days of immersion in a 3.5 wt% NaCl solution, the water absorption rate was recorded at only 2.15%. Electrochemical impedance spectroscopy (EIS) tests were performed on coatings with various additives. After 50 days of immersion in a 3.5 wt% NaCl solution, the low-frequency impedance modulus of the CS@M-T/SMP coating was four orders of magnitude greater than that of the pure SMP coating, maintaining a value of 1.80 × 10 9 Ω·cm², with a stable corrosion inhibition efficiency of 99.9%. In conclusion, this study effectively addressed the challenge of premature release of corrosion inhibitors in active/passive protective coatings, providing valuable insights for practical applications. Download: Download high-res image (152KB) Download: Download full-size image