Dynamic Bonds Facilitate the Microstructural Adaptation of Polyurethane to Attain Ultrahigh Fracture Energy

High fracture energy is crucial for engineering polymers, as it enhances safety, durability, and performance. However, the high-strength polymers commonly demanded in the engineering field often exhibit low fracture energy due to limited viscoelastic dissipation. Here, we developed a strategy for fabricating polyurethane that achieves both high strength and exceptionally high fracture energy by incorporating a combination of two extenders: the 4,4′-biphenol (PPDP) contains rigid biphenyl and isophthalic dihydrazide (IPDH) contains hydrazine, facilitating the formation of multiple hydrogen bonds. The synergistic effect of these chain extenders facilitates the reversible reconfiguration of hydrogen bonds, enabling microstructural adaptation during stretching. This process dissipates energy and promotes the growth of hard domains, thereby enhancing the load-bearing capacity of the polyurethane. Additionally, the growth of these hard domains helps to inhibit crack propagation, resulting in a fracture energy of up to 519.7 kJ m^–2 for the obtained MPU_0.75. This work provides a promising strategy that will guide the development of polymers with both high strength and high fracture energy.