Dual-Coordination Synergy in Polyurethane Hot-Melt Adhesives: Integrating Ultrahigh Strength, Self-Healing, and Extreme Environmental Tolerance

Thermoplastic polyurethane (TPU) hot melt adhesives have gained extensive applications in daily life and industry due to their simple operation, fast bonding speed, and ease of recycling. It is still challenging to produce a TPU hot melt adhesive with strong bonding strength and excellent environmental tolerance. Herein, a high-performance Cu2+-curcumin-pyridine-polyurethane (CDPU:Cu2+) TPU adhesive is reported, which introduces 2,6-diaminopyridine and curcumin to form dynamic metal–ligand bonds through Cu2+ cross-linking within the polyurethane system, resulting in a strong Cu2+-curcumin complex and a weak Cu2+-pyridine complex. This “strong-weak” dual coordination design enables the development of a tough, highly adhesive, self-repairable, and environmentally durable TPU adhesive. The tensile strength and elongation at break of this polyurethane hot melt adhesive can reach 40.06 MPa and 838%, respectively, demonstrating high bonding strength on various substrates. The lap shear strength of TPU on copper can reach 6.66 MPa. This adhesive exhibits self-healing capabilities, with a self-healing efficiency of up to 65% at 120 °C. Moreover, CDPUx:Cu2+ can achieve rapid self-healing under remote near-infrared laser (NIR) stimulation. It is noteworthy that the current TPU demonstrates excellent tolerance at the extremely low temperature of −196 °C and when exposed to various corrosive liquids. This polyurethane hot melt adhesive is expected to have broad prospects for withstanding extreme environments.