A Tough Metal-Coordinated Elastomer: A Fatigue-Resistant, Notch-Insensitive Material with an Excellent Self-Healing Capacity

Graphical Tough and stretchable : A metal-coordinated polyurethane complex was fabricated by complexing a simple pyridine-containing ligand with Fe 2+ ions The strong reversible coordination bond provides mechanical strength and the basis for self-healing. The complex possesses a very high tensile strength, and excellent self-healing efficiency of around 96 % of tensile strength at room temperature. The complex is notch-insensitive and possesses a very high fracture energy of 76186 J/m 2 . Self-healing materials can prolong device life, but their relatively weak mechanical strength limits their applications. Introducing tunable metal-ligand interactions into self-healing systems can improve their mechanical strength. However, applying this concept to solid elastomers is a challenge. To address this need, polyurethane-containing metal complexes were fabricated by introduction of a pyridine-containing ligand into polyurethane, and subsequent coordination with Fe 2+ . The strong reversible coordination bond provides mechanical strength and self-healing ability. By optimizing the monomer ratio and Fe 2+ content, the resulting complex possesses a very high tensile strength of 4.6 MPa at strain of around 498 % and a high Young's modulus (3.2 MPa). Importantly, the metal complex exhibits an extremely high self-healing efficiency of approximately 96 % of tensile strength at room temperature and around 30 % at 5 °C. The complex is notch-insensitive and the fracture energy is 76186 J/m 2 , which is among the highest reported values for self-healing systems.