Preparation of ecofriendly water-borne polyurethane elastomer with mechanical robustness and self-healable ability based on multi-dynamic interactions

Self-healing materials have attracted widespread attention owing to their capacity to extend the lifetime of materials and improve resource utilization. However, achieving superior mechanical performance and high self-healable capability simultaneously under moderate conditions remains a long-standing challenge. Integrating multiple dynamic interactions in waterborne polyurethane (WPU) systems can overcome the above-mentioned issue. Herein, environmentally friendly WPU systems containing multiple hydrogen bonds and boronic ester bonds in their polymer backbones were synthesized, where 2,6-diaminopyridine (DAP) and boric acid (BA) served as a dynamic chain extender and reversible cross-linking agent, respectively. The chain structure of the polymer was adjusted by controlling the ratio (DAP/BA) of hard segments, which could effectively meet the requirement of mechanical robustness and desirable self-healable efficiency. Benefiting from multiple dynamic interactions, the prepared WPU elastomer exhibited good mechanical properties, such as tensile strength (from 18.89 MPa to 30.78 MPa), elongation (about 900%) and toughness (from 54.82 MJ m^-3 to 92.74 MJ m^-3). Driven by water and heat, the IP-DAP₄₀-BA₁₀-WPU film cut in the middle exhibited good self-healing ability, with healing efficiencies of tensile stress of 90.74% and elongation of 91.29% after self-healing at 80 °C for 36 h. Meanwhile, the synthesized WPU elastomer exhibited good water resistance and thermal stability. This work presents a novel way to design robust self-healable materials, which will have wide promising applications in flexible electronics, smart coatings and adhesives.