Synthesis of Thermo-Shear-Responsive Dynamic Covalent Networks based on Humins and the Diels-Alder Reaction

Abstract

Humins are unavoidable by-products of biorefineries that convert sugars into functional platform chemicals. In this work, we present a strategy for utilizing them as reagents in Diels-Alder (DA) reactions. By leveraging their furan-rich structure, we demonstrate their principal reactivity with conventional dienophiles such as bismaleimides, which enables the formation of stable, reprocessable dynamic covalent networks. Notably, occurring cycloadditions are enantioselective yielding exclusively endo-adducts. Furthermore, these DA reactions display an unusual, reversed character, with the forward reaction proceeding at high temperature and the retro-DA reaction occurring at low temperature. The obtained materials exhibit tunable thermal and mechanical properties, self-healing behavior, and the potential for modulating electrical conductivity. Taken together, our findings establish a practical pathway for valorizing biorefinery side streams through the conversion of humins into high-performance materials.