A Biomass-Derived Imine-Linked Waterborne Polyurethane for Self-Healable Anticorrosive Coating

Waterborne polyurethanes (WPUs) have attracted increasing interest as coating materials due to their versatile performance and environmentally friendly characteristics. However, their durability and service life are often compromised by macroscopic damage or cracking caused by external forces. Here we report a castor-oil-based waterborne polyurethane (WPU) that covalently incorporates a rigid vanillin-derived monomer (PHAM) featuring reversible imine bonds. The reversible nature of dynamic imine bond endows the WPU with rapid, heat-triggered self-healing and recyclability; the rigidity of PHAM enables precise tuning of mechanical performance, achieving tensile strengths up to 25.9 MPa while retaining >250% elongation. To further investigate functionality, graphene-oxide (GO) nanosheets were dispersed in the WPU–PHAM matrix to fabricate ∼50 μm composite films. The combination of a densely packed GO/WPU barrier and the intrinsic imine-mediated healing imparts outstanding corrosion resistance. This work presents a versatile molecular-level strategy for coupling tunable mechanics, self-repair, and recyclability in biobased WPUs, and demonstrates its practical advantage in high-performance anticorrosion coatings.