Unveiling the potential of self-healing and closed-loop recyclability in bio-based non-isocyanate polyurethane

Abstract

The imperative shift towards sustainable production emphasizes the need for non-isocyanate polyurethanes (NIPUs) derived from biomass as a substitute for conventional petroleum-based polyurethanes. However, challenges persist in synthesizing NIPUs from renewable resources and addressing their recyclability post-service life. In this study, we report the synthesis of bio-based and closed-loop recyclable NIPU vitrimers using carbon dioxide (CO2), a vanillin derivative, and cystamine as bio-based feedstocks. The investigation examined the effect of the structure on the mechanical, thermal, and dynamic thermomechanical properties of bio-based NIPU vitrimers. The activation energy of the synthesized NIPUs was found to be relatively low (31.37 to 72.17 kJ/mol) after the incorporation of cystamine due to the presence of dual dynamic covalent bonds (disulfide and transcarbamoylation). As a result, the prepared bio-based NIPUs exhibited rapid self-healing and exceptional reprocessing efficiency (∼100 %). The mechanical properties of the reprocessed NIPUs could be restored to 99.5 % of their original values, highlighting remarkable reprocessing capabilities. The bio-based NIPU demonstrated closed-loop recyclability thanks to the dynamic disulfide bonds present in the vitrimer structure. This work offers an approach for the synthesis of bio-based NIPUS with closed-loop recyclability within the framework of sustainable materials.