To date, all epoxy vitrimer systems reported in the literature rely on addition of significant amounts of catalysts to achieve the dynamic transesterification reaction (TER). However, the catalysts used in vitrimers are often toxic and have poor miscibility with organic compounds, and they may further comprise the application performance like corrosion resistance. Moreover, the reprocessing and recycling properties are highly dependent on the loading amount and the type of catalyst. In this study, two hyperbranched epoxy (HBE) prepolymers are synthesized and then reacted with succinic anhydride to prepare a catalyst-free epoxy vitrimer system. It is demonstrated that both the curing during the preparation of the cross-linked materials and the TER in the resulting cross-linked materials proceed properly without addition of external catalyst. We attributed this phenomenon to the abundant free hydroxyl groups in HBE which serve as both reacting moiety and catalyst in both curing and the TER processes. At elevated temperatures (>120 °C), the TER is activated to enable fast stress relaxation of the cross-linked network. In addition, the epoxy vitrimers exhibit glass transition temperatures (T g’s) in the range 70–96 °C, excellent thermostability, and mechanical properties similar to those of the traditional epoxy materials. By taking advantages of these features, we also demonstrate a promising self-healable and catalyst-free coating.

Conventional epoxy polymers are constructed by petro-based resources that are toxic and nonrenewable, and their permanent cross-links make them difficult to be reprocessed, reshaped, and recycled. In this study, a unique eugenol-derived epoxy (Eu-EP) is synthesized, and then vitrimeric materials are prepared by reacting Eu-EP with succinic anhydride (SA) at various ratios (1:0.5, 1:0.75, and 1:1) in the presence of zinc-containing catalysts. All vitrimers exhibit excellent shape changing, crack healing, and shape memory properties. Although vitrimers with 1:0.75 and 1:1 ratios cannot be physically reprocessed, they can be well reprocessed by the chemical method of being simply decomposed in a benign ethanol solution without loading additional catalyst. The collected decomposed polymers can form vitrimers again after exposure at 190 °C for 3 h. This work combines the concepts of vitrimer preparation, chemical recycling, and biobased polymer together, which would bring a feasible way to satisfy the demands of sustainability.

The design of high glass transition temperature (T g ) thermoset materials with considerable reparability is a challenge. In this study, a novel biobased triepoxy (TEP) is synthesized and cured with an anhydride monomer in the presence of zinc catalyst. The cured TEP exhibits a high T g (187 °C) and comparable strength and modulus to the cured bisphenol A epoxy. By adopting the vitrimer chemistry, the cross-linked polymer materials are imparted significant stress relaxation and reparability via dynamic transesterification. It is noted that the reparability is closely related to the repairing temperature, external force, catalyst content, and the magnitude of rubbery modulus of the sample. The width of the crack from the cured TEP can be efficiently repaired within 10 min. This work introduces the first high-T g biobased epoxy material with excellent reparability and provides a valuable method for the design of high-T g self-healing materials suitable for high service temperature.

This work introduces a simple and green method for the preparation of a fully biobased vitrimer material and demonstrates a potential application for recoverable adhesives.

Early epoxy vitrimers in the literature rely on an inequivalent epoxy/anhydride stoichiometry and a large amount of catalyst to achieve a decent transesterification rate within the crosslinked network. This design approach raises a number of concerns such as poor miscibility of the catalyst with other ingredients, poor mechanical properties owing to insufficient crosslinking, the toxicity of the catalyst, etc. In this study, a hydroxyl-amine compound, triethanolamine (TEOA), is incorporated as a catalytic co-curing agent to a typical BPA epoxy–cyclic anhydride curing system to give a TEOA-mediated covalent adaptable network system. The hydroxyl groups and tertiary amine of TEOA catalyze the curing process, and the tertiary amine and the regenerated hydroxyls in the crosslinked network accelerate dynamic transesterification. The resulting epoxy vitrimer exhibits a high glass transition temperature (∼135 °C), excellent tensile strength (∼94 MPa), and fast repairing rate (10 min at 190 °C). Recycling of the TEOA-mediated epoxy vitrimer and reuse of the recyclate are also studied. In an experiment, the vitrimer is ground into powder, and in another, it is degraded in an aqueous solution. The recyclates collected from both experiments are incorporated into the fresh resin, and the new vitrimer materials exhibited similar T gs and moduli to that of original vitrimer samples. This work provides a solution to eliminate the performance gap between conventional epoxy and epoxy vitrimer and offers simple recycling methods of epoxy vitrimer for new epoxy.