Lignin-derivable, thermally healable thiol-acrylate vitrimers with improved mechanical performance and reprocessability via transesterification

Abstract

The development of vitrimers with dynamic covalent bonds enables reprocessability in crosslinked networks, offering a sustainable alternative to conventional thermosets. In this work, a thiol-acrylate vitrimer was synthesized from lignin-derivable (bis)phenols (guaiacol and bisguaiacol F) and compared to a control derived from petroleum-based precursors (phenol and bisphenol F) to investigate the effect of structural differences on network properties and thermal reprocessing. The presence of methoxy groups in the lignin-derivable vitrimer promoted intermolecular interactions by serving as additional hydrogen bonding acceptors during curing, leading to a denser network, as evidenced by a higher rubbery storage modulus (∼2.4 MPa vs. ∼1.4 MPa) and glass transition temperature (∼34 °C vs. ∼28 °C). The lignin-derivable vitrimer exhibited a slightly higher elongation-at-break (∼170% vs. ∼130%) and improved mechanical robustness, including a nearly two-fold increase in Young's modulus (∼6.9 MPa vs. ∼3.4 MPa) and toughness (∼750 kJ m⁻³vs. ∼390 kJ m⁻³). The similar stress relaxation behavior and activation energy of viscous flow indicated comparable bond exchange dynamics between the two vitrimers, while the lignin-derivable system demonstrated higher thermal healing efficiency with improved recovery of tensile properties after reprocessing. These findings highlight the potential of lignin-based aromatics in designing mechanically robust and sustainable vitrimers, aligning with efforts to develop renewable and reprocessable polymeric materials.