Bio-based imine- and disulfide-containing epoxy vitrimers with practical self-healing properties at room temperature

Bio-based vitrimers have attracted considerable attention because of their carbon neutrality, healability, and recyclability, which contribute to resource saving and energy saving. The reactions of vanillin with cystamine and 1,6-diaminohexane yielded a phenolic hardener containing both imine and disulfide groups (DVNCTA) and a phenolic hardener containing only imine groups (DVNDAH), respectively. These hardeners were utilized to cure epoxy resin mixtures comprising bio-based polyglycerol polyglycidyl ether (PGPE) and petroleum-based flexible poly (ethylene glycol) diglycidyl ether (PEGDGE) in varying molar ratios. The cross-linking density, glass transition temperature, and mechanical strength of the DVNCTA-cured epoxy vitrimers diminished as the ratio of PGPE to PEGDGE decreased. Remarkably, all cured products underwent at least three successful self-healing cycles by standing at room temperature for 24 h. The tensile strength-based healing efficiency ( η σ ) of the DVNCTA-cured epoxy vitrimers improved with decreasing PGPE to PEGDGE ratios, reaching a maximum η σ (100%) at PGPE/PEGDGE ratio of 1/2. Notably, when comparing DVNCTA- and DVNDAH-cured epoxy vitrimers with identical PGPE/PEGDGE ratios, the former exhibited significantly superior healing performance.