Waterborne polyurethane (WPU) with self-healing properties is highly desirable for sustainable development. However, balancing the mechanical and self-healing properties of WPU is challenging. In this study, ultrahigh mechanical and self-healing performance was simultaneously achieved by introducing dopamine-modified iron-oxide nanoparticles (Fe₃O₄@DA NPs) to a WPU matrix consisting of soft poly(tetramethylene ether) glycol segments and hard isoforone diisocyanate and dimethylolpropionic acid segments. Consequently, the tensile strength and toughness of the WPU/Fe₃O₄@DA composite increased to 63.6 MPa and 179.35 MJ·m^–3, respectively; these values correspond to improvements of 276% and 403% over those of pure WPU (16.9 MPa and 44.50 MJ·m^–3, respectively). The proposed composite also exhibited excellent self-healing ability at room temperature; that is, the stress and strain self-healing efficiencies after 6 h at 60 °C increased by 93.5% and 100%, respectively. This performance was achieved because the Fe₃O₄@DA NPs, which acted as reinforcing fillers, interacted strongly with the hard WPU segments via the covalent reaction of the DA amine groups with the WPU-matrix isocyanate groups, remarkably enhancing mechanical properties. Moreover, catechol–Fe(III) coordination bonds formed between the DA and Fe₃O₄ NPs, which promoted relaxation behavior and, thus, enhanced the self-healing efficiency. The approach presented in this study constitutes an effective strategy for developing an efficient self-healing polymer with high mechanical strength, which can endow self-healing coatings and adhesives with long service life in severe environments.

中文翻译：

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水性聚氨酯复合材料的超强机械和自修复性能


具有自修复特性的水性聚氨酯 （WPU） 是可持续发展的理想选择。然而，平衡 WPU 的机械和自愈特性具有挑战性。在这项研究中，通过将多巴胺改性的氧化铁纳米颗粒 （Fe₃O₄@DA NPs） 引入由软聚（四亚甲基醚）二醇链段和硬异咯酮二异氰酸酯和二羟甲基丙酸链段组成的 WPU 基质中，同时实现了超高的机械和自愈性能。因此，WPU/Fe₃O₄@DA复合材料的拉伸强度和韧性分别提高到63.6 MPa和179.35 MJ·m^–3;这些值对应于比纯 WPU（分别为 16.9 MPa 和 44.50 MJ·m^–3）提高 276% 和 403%。所提出的复合材料在室温下也表现出优异的自修复能力;即在 60 °C 下 6 h 后，应力和应变自愈效率分别提高了 93.5% 和 100%。之所以能实现这一性能，是因为作为增强填料的 Fe₃O₄@DA NPs 通过 DA 胺基团与 WPU 基体异氰酸酯基团的共价反应与硬质 WPU 链段强烈相互作用，显著提高了机械性能。此外，儿茶酚-Fe（III） 配位键在 DA 和 Fe₃O₄ NPs 之间形成，促进了松弛行为，从而提高了自愈效率。本研究中提出的方法构成了开发具有高机械强度的高效自修复聚合物的有效策略，该聚合物可以赋予自修复涂层和粘合剂在恶劣环境中较长的使用寿命。