Preparation of renewable gallic acid-based self-healing waterborne polyurethane with dynamic phenol-carbamate network: toward superior mechanical properties and shape memory function

Endowing thermoset self-healing polymers with excellent mechanical properties and shape memory function by utilizing bio-based monomers is highly desirable for the development of the next-generation smart materials. To achieve this goal, herein, we developed a novel thermally induced self-healing system with robust mechanical properties and shape memory function by incorporating dynamic phenol-carbamate bond formed by the polymerization reaction of the renewable gallic acid (GA) and isocyanate into waterborne polyurethane (GA-WPU) with excellent emulsion stability. The mechanical properties and thermal stability of the resulting polymers were much improved due to the introduction of phenol-carbamate networks. Moreover, the crystallization and microphase separation were evaluated to deeply insight into the effect of GA moieties incorporated into the polymer chains of GA-WPU. Significantly, a good balance can be achieved between desirable self-healing ability (healing efficiency 81.1%) and robust mechanical properties (tensile strength 45.1 MPa and elongation at break 576.5%) by adjusting dynamic phenol-carbamate bonds incorporated into the polymer networks, and compared with the reported self-healing polymers, the recovered tensile strength of our target polymer shows an overwhelming superiority. Furthermore, taking the advantage of the crystalline PBA (switching segment) and phenol-carbamate cross-linkages, the prepared GA-WPU polymer can rapidly recover from temporary shape to original shape by thermal energy (less than 30 s, and the shape fixity and recovery ratio remain above 91.5%). We envision that this elaborate strategy is instructive for designing mechanically robust polymeric materials with self-healing, shape memory function and environmentally friendly characteristics. [GRAPHICS] .

Automated summary

This study develops a thermally induced self-healing system with robust mechanical properties and shape memory function by incorporating dynamic phenol-carbamate bonds formed by renewable monomers into waterborne polyurethane. By adjusting the content of phenol-carbamate bonds, a good balance is achieved between self-healing ability and robust mechanical properties.