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
MPU0.75. This work provides a promising strategy that will guide the development of polymers with both high strength and high
fracture energy.