Functional bio-based vitrimer with excellent healing and recyclability based on conjugated deflection self-toughening

The three-dimensional network crosslinking structure of a vitrimer provides excellent mechanical strength and thermal stability, which are crucial for practical applications. However, achieving a harmonious balance between rigidity and toughness presents coordination difficulties that impede their broad applications. Herein, we propose a new regulatory strategy for high toughness using a functional vitrimer based on vanillin and dihydroxy fatty monoamines. The electron delocalization effect of the conjugated structures was used to coordinate the design of the crosslinking points to adjust the topological transformation temperature of the materials. The conjugate complement of the rigid benzene ring and imine bond caused a shift in the electron cloud distribution in the material, which effectively lowered the energy barrier for the exchange of imine bonds in the crosslinked network. The imine bond dissociation energy decreased from 170.75 to 97.80 kcal/mol compared with the uniform conjugation. The exchange rate of dynamic covalent bonds was accelerated at the same temperature, which is conducive to the functionalization of materials under realistic conditions. The strain in the vitrimer obtained in this study increased significantly under the action of external forces. Furthermore, the crosslinking density of the system was improved using multiple epoxy groups to avoid stress loss. The vitrimer obtained in this study exhibited a tensile strength of 35.6 MPa and an elongation at break of 247.7%. In addition, the synthesized vitrimer showed excellent welding, healing, and shape memory performance.