Autonomous self-healing supramolecular elastomer reinforced and toughened by graphitic carbon nitride nanosheets tailored for smart anticorrosion coating applications

Intrinsic self-healing materials possessing the capability to autonomously repair their structure and functionalities upon mechanical damage have attracted great attention. Up to now, despite intense research in this area, the synthesis of intrinsic self-healing materials with a simultaneous combination of stiffness, strength and toughness is still a huge challenge. Herein, inspired by nature, we prepared a novel poly(urea-urethane)-graphitic carbon nitride nanosheet (PUU-g-C3N4 NS) composite material, in which the multiple hydrogen bonds within the PUU matrix endow the composite material with room temperature self-healing ability, and g-C3N4 NSs, serving as both chemical and physical cross-linkers, provide the composite material with significantly improved mechanical properties. The PUU-g-C3N4 NS material was subsequently deposited onto the surface of aluminum alloy 2024 as a smart anticorrosion coating (AC) by the drop-casting method for protection. The anticorrosion performance as well as the self-healing ability of the PUU-g-C3N4 NS AC was evaluated by electrochemical impedance spectroscopy, laser microscopy and scanning Kelvin probe technology. The experimental results show that the PUU-g-C3N4 NS AC maintained its protective capability even after immersion in 0.5 M NaCl for 20 days. Moreover, an artificial scratch on the surface of the PUU-g-C3N4 NS AC was observed to vanish and the regenerated anticorrosion ability in the damage area was gained after healing for only 10 min. The introduction of g-C3N4 NSs makes the PUU-g-C3N4 NS composite material meet the applicable requirements forAC, offers the composite coating excellent anti-penetration ability and retains the satisfactory autonomous self-healing function under ambient conditions, even under high humidity.