Rice husk cellulose fiber-derived vitrimers: dynamic covalent network design via transesterification exchange with hierarchical structure preservation

Bio-based vitrimers have gained considerable attention for their potential to replace fossil derived plastics, address end-of-life recycling issues through dynamic covalent chemistry, and ultimately align materials science with sustainable development principles. However, conventional bio-based vitrimers necessitate the complete depolymerization of natural polymers into small-molecule precursors, disrupting the native supramolecular architecture that underpins their mechanical performance. This study introduces a strategy that preserves the intrinsic fibrous structure of rice husk cellulose to create high-performance, reprocessable vitrimers. Rice husk fibers were activated via steam explosion-alkaline treatment and functionalized through in-situ esterification to incorporate acetyl and phthaloyl groups, while largely preserving the polymerization degree. Crosslinking with bisphenol A diglycidyl ether generated a β-hydroxyester dynamic network. In contrast to a control vitrimer made from cellulose acetate phthalate (CAP) small molecules, the fiber-reinforced vitrimer (ERH-Vitrimer) exhibited superior mechanical properties and thermal stability, owing to the preserved cellulose framework. The ERH-Vitrimer demonstrated reprocessability without external catalyst addition, maintaining over 90% of its tensile strength after 5 cycles, significantly outperforming CAP-Vitrimer, in addition to offering advantages in cost efficiency and biomass content. This work thus demonstrates that preserving native supramolecular structures in bio-based vitrimers leads to a combination of enhanced thermal stability, mechanical robustness, and sustainable reprocessability.