The global production of thermosets has been increasing in recent years, causing rapid consumption of fossil-based feedstocks and contributing to the plastic waste accumulation in the environment, especially because they cannot be easily reprocessed or recycled at the end of their lifetime. To overcome those issues, dynamic crosslinks capable of exchange reactions can be introduced, enabling network rearrangements, malleability, and reprocessability [1]. Those dynamic thermosets form a new class of materials, called vitrimers, since they flow like a vitreous silica (quartz glass) following the Arrhenius law [2]. At service temperatures they behave like permanently crosslinked polymers but at elevated temperatures the exchange reactions speed up making flow possible while maintaining constant number of chemical bonds and crosslinks. Thanks to that, vitrimers can be repaired, reshaped and reprocessed decreasing significantly the cost and environmental impact. 

Facile way to produce biobased vitrimers from vegetable oils and a diboronic ester dithiol vitrimer crosslinker will be presented [3]. The synthesis of the cross-linker and the production process of the vitrimers has been done following green chemistry principles. The developed vitrimer materials can be reprocessed multiple times like a thermoplastic, without compromising its mechanical properties. Moreover they can be conveniently recycled by reversible hydrolysis in 90% ethanol and subsequent solvent evaporation, regenerating the original vitrimer. In case of an accidental release into the environment, the materials are able to biodegrade, solving the problem of waste accumulation. Properties of the final materials can be tuned from soft and flexible to rigid and hard by varying the vegetable oil type and crosslink density. The use of those materials in self-healing coatings, strain sensors and carbon fiber composites will be demonstrated.

References

1. D. Montarnal, M. Capelot, F. Tournilhac, L. Leibler, Science, 2011, 334 (6058), 965.

2. W. Denissen, J. M. Winne, F. E.Du Prez, Chemical Science, 2016, 7 (1), 30-38.

3. A. Zych, J. Tellers, L. Bertolacci, L. Ceseracciu, L. Marini, G. Mancini, A. Athanassiou, ACS Applied Polymer Materials, 2021, 3 (2), 1135–1144.