Mechanically Robust Poly(urethane‐urea) Elastomers Under Extreme Temperatures, Humidity, and Solvent Exposure

ABSTRACT Poly(urethane‐urea) (PUU) elastomers crosslinked by hydrogen bonds have high mechanical properties, making them a great candidate for high‐performance thermoplastic elastomers (TPEs). However, due to the dynamic nature of hydrogen bonds, they are easily affected by heat, water, or solvents, resulting in rapid mechanical degradation. Herein, we report a robust PUU elastomer constructed from polycaprolactone (PCL), hexamethylene diisocyanate (HDI), and dodecanedioyl dihydrazide (DD). Our design leverages the conformational flexibility of HDI and DD to enable efficient packing of carbamate and acylsemicarbazide groups in hard segments. By increasing their content, the total number of hydrogen bonds is significantly enhanced without sacrificing bonding efficiency, yielding more cohesive and stable hard‑segment clusters that can resist degradation by heat, water, or solvents. The optimized PCL‑1.67DD exhibits ultra‑high mechanical properties, with a tensile strength of 77.7 MPa, toughness of 629.8 MJ m −3 , and fracture energy of 642.3 kJ m −2 . Notably, PCL‑1.67DD retains excellent performance at extreme temperatures, demonstrating a high toughness of 264.2 MJ m −3 at 120°C. The material shows negligible swelling in water across pH 2‐12 and exceptional resistance to diverse organic solvents. Additionally, PCL‐1.67DD demonstrates excellent degradability and recyclability. These findings present a versatile strategy for next‑generation TPEs with combined mechanical robustness, environmental stability, and sustainability.