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.

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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.