The synthesis of polymeric materials that simultaneously possess multiple excellent mechanical properties and high-efficient self-healability at room temperature is always a huge challenge. Here, we report the synthesis of a transparent polyurea material that can self-heal at room temperature with the aid of water and, meanwhile, has multiple remarkable mechanical performances, including super-high strength, excellent toughness, and large stretchability. Thanks to the synergistic enhancement of both dynamic imine bonds and hierarchical hydrogen bonds within the networks, the resulting polyureas have a world-record tensile strength of 41.2 MPa when compared with other polyurethanes that can self-heal at room temperature and, at the same time, a large breaking strain of 823.0% and a superior toughness of 127.2 MJ/m3. Besides the influence of imine bonds, the mechanical properties of the polyureas are also strongly related to the density and strength of the hierarchical hydrogen bonds within the polyurea networks, and these two factors could be finely controlled by adjusting the mass ratio of the soft segments with different chain lengths and the types of diisocyanates used for polyurea synthesis, respectively. More importantly, the highly dynamic characteristic of both imine bonds and hierarchical hydrogen bonds within the polyureas endows the materials with repeated water-enabled room-temperature self-healing capacity with a high healing efficiency of 92.2%. Moreover, the polyureas can also be recycled or remolded under mild conditions by the hot-pressing or dissolution/casting process. The synthesized polyureas also show great potential in damping applications with a loss factor larger than 0.3 over the temperature range from 12 to 75 °C. It is believed that polyureas with super-high and well-tunable mechanical properties and high-efficient room-temperature self-healing ability have great potential to substitute traditional irreparable polymers in diverse practical applications.
Wei-Chen Zhou,Xue-Qin Gao,Jia-Hao Li,Gui-Lin Hu,Yu-Zhong Wang,Cong Deng
Covalent Adaptive Networks (CANs), especially when assisted by sacrificial bonds or fillers, present a compelling strategy to achieve simultaneous high-performance and recyclability in rubbers. However, CAN-based rubbers often suffer from limited extensibility. Weak interactions acting as crosslinking points have shown surprising performance reversal in thermalplastic elastomers, but the design of non-covalently crosslinked rubbers with high mechanical strength remains a significant challenge. In this study, we present an effective approach totally depending on weak interactions to develop a bio-based epoxidized natural rubber (ENR), modified with carboxylic acid-functionalized 2-ureido-4-pyrimidinone (UPy-COOH), which forms a hierarchical hydrogen bonding network (ENR-UPy). The cohesive energy, energy dissipation, and dynamic responsiveness provided by the hierarchical hydrogen bonding network, coupled with strain-induced crystallization (SIC) of ENR, enable ENR with exceptional extensibility, surpassing CANs-based rubbers while maintaining robust mechanical strength. The optimized ENR-UPy exhibits outstanding elongation of 1190 % at break and toughness of 62.00 MJ/m 3 while maintaining high tensile strength of 11.87 MPa. More importantly, the dynamic nature of this hierarchical hydrogen bonding network enables reprocessed ENR-UPy to recover 99 % and 96 % tensile strength and elongation respectively, remarkably superior to reprocessability of CANs-based rubbers, and totally different from the non-renewable characteristics of conventional vulcanized rubbers. This work highlights the potential of hierarchical hydrogen bonds in creating reprocessable rubbers, offering a sustainable solution to the challenges of rubber waste and advancing green fabrication technologies.
危险品化学品经营许可证（带存储）