Self-healing bio-based epoxy films based on dynamic covalent bond synergy under conditions of pH response

A novel bio-based epoxy film with excellent mechanical properties and self-healing capabilities at room temperature was successfully synthesized from thioctic acid (TA) and poly(ethylenimine) (PEI). Disulfide, amide and ester bonds were incorporated into epoxy system to form a dynamic covalent network, which greatly improves the mechanical properties, cross-linking density, and self-healing performance of epoxy film. The structure and properties of the bio-based epoxy films (TPTs) were thoroughly analyzed and discussed in depth. The bio-based epoxy film exhibited the high gel fraction (~80 % at 72 h) and high thermal stability (>260 °C at T 5% ). Furthermore, the bio-based epoxy film showed an increase of approximately 243 % in tensile strength, 1681 % in Young's modulus compared to the original product. Additionally, the film exhibited exceptional self-healing performance with a healing efficiency of 96 % during the pH = 3 solutions at room temperature. Molecular dynamics simulation and Situ infrared spectra indicated that the reorganization of dynamic disulfide bonds spontaneously occurred after breaking and then induced the responsible repair process of the film. This research provides a methodology for developing bio-based, low-cost, and high-performance materials. The developed dynamic covalent epoxy network demonstrates significant potential for practical applications requiring long-term durability and high reparability, such as protective coatings, high-performance adhesives, and durable composite matrices. • A novel self-healing bio-based epoxy film was successfully created. • Multiple dynamic covalent bonds synergy play an important role on the structure and properties of bio-based epoxy films. • The films exhibit exceptional self-healing performance with a healing efficiency of 96% during the pH=3 solutions. • The bio-based epoxy films had outstanding mechanical properties. • Molecular dynamics simulation indicate that the reorganization of dynamic disulfide bonds is spontaneous.