Shi Zhen, Kang Jing, Zhang Ling
State Key Laboratory of Supramolecular Structure and Materials, College of Chemistry, Jilin University, Changchun 130012, P. R. China.
ACS Appl Mater Interfaces. 2020 May 20;12(20):23484-23493. doi: 10.1021/acsami.0c04414. Epub 2020 May 7.
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/m. 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.
同时具备多种优异机械性能并在室温下具有高效自修复能力的聚合物材料的合成一直是一项巨大挑战。在此，我们报道了一种透明聚脲材料的合成，该材料在水的辅助下可在室温下自修复，同时具有多种卓越的机械性能，包括超高强度、优异韧性和大拉伸性。得益于网络中动态亚胺键和分级氢键的协同增强作用，与其他可在室温下自修复的聚氨酯相比，所得聚脲具有41.2 MPa的世界纪录拉伸强度，同时具有823.0%的大断裂应变和127.2 MJ/m的优异韧性。除了亚胺键的影响外，聚脲的机械性能还与聚脲网络内分级氢键的密度和强度密切相关，这两个因素可分别通过调整不同链长的软段质量比和用于聚脲合成的二异氰酸酯类型来精细控制。更重要的是，聚脲中亚胺键和分级氢键的高动态特性赋予材料具有92.2%的高修复效率的重复水基室温自修复能力。此外，聚脲还可通过热压或溶解/浇铸工艺在温和条件下进行回收或重塑。合成的聚脲在12至75 °C的温度范围内损耗因子大于0.3，在阻尼应用中也显示出巨大潜力。据信，具有超高且可良好调节的机械性能和高效室温自修复能力的聚脲在各种实际应用中具有替代传统不可修复聚合物的巨大潜力。
