Polyurethane Elastomer with Unprecedented Thermostability, Long‐Cycle Antifatigue, and Ultrafast Self‐Healing Capability

Abstract Elastomers play important roles in major equipment, mega facilities, and other advanced applications. However, in practical applications, it is often subjected to extreme environmental conditions, such as repeated cyclic mechanical loading, high temperatures, external impacts, etc. Designing an elastomer with high strength/toughness and resistant to fatigue is particularly challenging. Herein, a novel polyurethane elastomer is developed, consisting of ascorbic acid‐based chemodynamic covalent adaptive networks (A‐CCANs). The keto‐enol dynamic chemistry and dynamic carbamate bonds within A‐CCANs endow the elastomer with unprecedented thermostability (thermal decomposition temperature up to 345 °C, comparable to well‐known PTFE), excellent mechanical properties (true fracture stress reaches 0.88 GPa) and impact resistance (able to withstand a stress of 268.3 MPa when the surface is compressed to 99.9%, while absorbing 68.93 MJ m⁻³ of energy), as well as sterling fatigue resistance (residual strain less than 0.02 after 20 000 cycles). Besides, A‐CCANs also feature rapid (∼1 s) self‐healing capability and reprocessability (recycling efficiency up to 90%). This study provides new ideas for compromising between the stability and responsiveness of polymers, which have groundbreaking significance in engineering applications such as smart devices and structural materials.