Recyclable epoxy vitrimers based on multimechanism-activated transesterification strategies for photothermal conversion and self-healing materials

The intrinsically slow relaxation, poor toughness, and limited reprocessability of transesterification-based epoxy vitrimers make it difficult to meet the performance demands of self-healing materials and sustainable development goals. Herein, glutamic acid (Glu) and formic acid (FA) are incorporated into a sebacic acid-cured epoxy network via a stepwise curing protocol, enabling the construction of Glu/FA-modified epoxy vitrimers (GFEVs) with rapid stress relaxation induced by multiple accelerating mechanisms. Glu supplies tertiary amine catalytic sites but reinforces the network, while FA helps to dissolve Glu and participates in curing to form primary ester bonds which reduce the degree of cross-linking, thereby synergistically accelerating transesterification reactions. By varying the ratio of curing agents, GFEVs exhibit adjustable stress relaxation and mechanical properties. GFEV10 containing FA and a 10 mol% Glu shows a relaxation time of 35.2 s at 180 °C, approximately a 3.6-fold reduction relative to unmodified epoxy vitrimer. The tensile strength and elongation at break increase to 21.9 MPa and 236.9%, respectively. Besides, the significantly accelerated transesterification reactions enable excellent reprocessability and shape memory behavior of GFEV10. After three reprocessing cycles, the recycling efficiency still maintained above 80%. Integrating carbon nanotubes (CNTs) with GFEV10 imparts photothermal effect and the prepared CNTs/epoxy vitrimer composites (CNTs/GFEVs) display near-infrared triggered photothermal self-healing and welding, together with rapid degradation performance.