Hybrid bio-based epoxy vitrimers: balancing high performance and recyclability for sustainable innovation

The development of vitrimers has been gaining great interest lately, since the presence of dynamic covalent bonds in their structure allows the rearrangement of their topology, which leads them to combine the great properties characteristic of thermoset materials with the recyclability proper of thermoplastics. This duality is highly relevant for replacing conventional fossil-based epoxy resins with more sustainable alternatives. Moreover, the possibility of using bio-based precursors for their preparation is also an option in order to obtain an even more environmentally friendly material. In this work, partially and fully bio-based vitrimers were prepared using citric acid and two trifunctional epoxy resins: an aromatic fossil-based resin (GOA) and a linear bio-based resin (GGE). Fully bio-based systems exhibited very low glass transition temperatures (T_g ≤ 24 °C) and poor rigidity, limiting their applicability. However, hybrid systems that incorporated both epoxy resins achieved a remarkable balance between rigidity and ductility. In particular, the 0.7GOA/GGE formulation (71 wt% bio-based) cured at 120 °C exhibited a T_g of 43 °C, a flexural modulus of ∼2400 MPa, and a toughness over four times higher than the fully fossil-based counterpart. The recyclability of all systems was confirmed through thermo-mechanical and chemical routes, although higher GGE content required more severe conditions. All networks displayed shape-memory properties, demonstrating the versatility of these materials. These results highlight hybridization as an effective and scalable strategy to reconcile high bio-based content with strong mechanical performance and recyclability, positioning these vitrimers as sustainable candidates for advanced functional applications.