Epoxy Vitrimer with Excellent Mechanical Properties and High Tg for Detachable Structural Adhesives

Abstract

It is a long-standing challenge for thermoset resins to simultaneously achieve outstanding thermomechanical and mechanical properties as well as rapid network reconfiguration due to the trade-off between chemical bond transformation and stability of the network. The design of the vitrimer network topology is an effective strategy to address the above issues. Here, we prepared an epoxy vitrimer material (DGEBA–API–MHHPA) with excellent mechanical properties and high glass-transition temperature (T_g) by introducing rigid-flexible integrated side chains [1-(3-aminopropyl) imidazole (API)], which endow DGEBA–API–MHHPA multiple interactions including “internal antiplasticization” effect, intermolecular hydrogen bonds, and π–π interactions. Moreover, the introduction of Zn²⁺ facilitates transesterification, enabling the fast rearrangement of the network. Specifically, the relaxation time of DGEBA–API_0.2–MHHPA_0.8–Zn reaches 65 s at 200 °C. Meanwhile, Zn²⁺–imidazole coordination bonds with energy dissipation improve the toughness of the vitrimer network. The resulting DGEBA–API_0.2–MHHPA_0.8–Zn exhibits self-healing and recyclable behaviors and possesses 80.3 MPa of tensile strength, 3.25 GPa of Young’s modulus, 7.2 MPa·m^1/2 of fracture toughness (K_IC), and T_g of 129 °C. Concurrently, DGEBA–API_0.2–MHHPA_0.8–Zn can be applied as detachable structural adhesives for various substrates and can be used as matrixes of recyclable and electrically self-healing composites. This skillful strategy can be widely referenced in the large-scale manufacturing of high-performance dynamic covalent epoxy resins and their composites with excellent mechanical and thermomechanical performance.