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Traditional impact-resistant plastics become brittle at low temperatures due to restricted polymer chain mobility, rendering them unsuitable for cryogenic applications. Developing ultra-tough plastics with superior impact resistance under extreme low-temperature conditions remains a significant challenge. Here, this study reports the fabrication of ultra-tough, impact-resistant poly(urea-urethane) (PUU) plastics by cross-linking soft poly(tetramethylene ether glycol) (PTMEG) chains through multiple types of hydrogen bonds and hydrogen-bond aggregates with varying binding energies. The PUU plastic features a bicontinuous phase-separated nanostructure, where hydrogen-bond-cross-linked, rigid yet deformable domains are interpenetrated with soft PTMEG chains. At -50 °C, the plastic exhibits mechanical properties comparable to those of ultra-tough, high-strength plastics at ambient temperature, with yield strength of 81.1 MPa, breaking strength of 133.0 MPa, Young's modulus of 1.5 GPa, and breaking strain of 220.9%. A 0.3-mm-thick sample achieves a maximum impact force of 667.8 N and an impact energy of 3.8 J at -50 °C, while maintaining exceptional mechanical robustness and flexibility even at -196 °C. The low-temperature toughness and impact resistance of the PUU plastics surpass those of existing impact-resistant plastics. This study demonstrates that hydrogen bonds with a broad spectrum of binding energies serve as ideal cross-links for fabricating ultra-tough, impact-resistant plastics suitable for cryogenic applications.
Wang et al. (Wed,) studied this question.