Self-healing bio-based epoxy vitrimers containing dual dynamic vinylogous urethane and disulfide bonds

Bio-based vitrimers have attracted considerable attention owing to their carbon neutrality, and dynamic covalent bond exchange, which can enable self-healing and reprocessing. In this study, bio-based epoxy vitrimers containing dual dynamic vinylogous urethane and disulfide bonds were prepared through the thermal curing of polyglycerol polyglycidyl ether (PGPE), glycerol tris(acetoacetate) (GLAA), cystamine (CTA), and dimer diamine (DDA, Priamine™ 1075). The resulting vitrimer films were designated as VUE-C/D- a / b , where a / b represents the amine molar ratio of CTA to DDA ( a / b = 0/4, 1/3, 2/2, 3/1). For comparison, an epoxy vitrimer containing only vinylogous urethane bonds (VUE-H/D-1/3) was prepared under the same conditions as VUE-C/D-1/3 except that hexamethylene diamine (HMDA) was used instead of CTA. The glass transition temperature ( T g ), tensile modulus, and tensile strength of the VUE-C/D films increased with increasing feed CTA/DDA ratio. Compared with VUE-C/D-1/3, VUE-H/D-1/3 exhibited higher tensile modulus and tensile strength but a slightly lower T g . Stress relaxation experiments showed that VUE-C/D-1/3 exhibited a shorter relaxation time than VUE-H/D-1/3 at 100–140 ℃. All cured films exhibited self-healing behavior and could be healed at least three times by hot-pressing at 140 ℃ for 3 h under 0.5 MPa. Among the cured films, VUE-C/D-1/3 exhibited the highest healing efficiency ( η σ = 86%) in terms of tensile strength recovery, whereas VUE-H/D-1/3 showed a lower η σ (63%). These results demonstrate the beneficial effect of combining vinylogous urethane and disulfide dynamic bonds on the self-healing performance of highly bio-based epoxy vitrimers.