Mechanically Robust and Recyclable Diels-Alder Networks from a Degradable Cellulose-Based Matrix

Designing sustainable polymer materials that combine mechanical robustness with recyclability remains a significant challenge. Here, we report a cellulose-based Diels-Alder (DA) cross-linked network that integrates structural strength, thermoreversible recyclability, and tunable biodegradability. Cellulose was functionalized with furfurylamine via carbamate formation to introduce furan moieties while minimizing perturbation of its π-electron system, yielding furfuryl carbamate cellulose (FC). By controlling the degree of substitution, FC was designed to enable efficient cross-linking through DA reactions while preserving the inherent biodegradability of cellulose. The DA cross-linked networks were prepared by reacting FC with 1,6-bis-(maleimido)-hexane (BMI) via solvent casting. The resulting films exhibited tunable mechanical properties with increasing BMI content, with Young's modulus ranging from 0.4 to 3.1 GPa and maximum stress ranging from 20 to 56 MPa, while maintaining relatively high toughness. Chemical recycling was enabled through thermally induced retro-DA reactions in solution, followed by reformation from solution. Enzymatic degradation tests using cellulase showed that uncross-linked FC degraded rapidly, whereas cross-linked networks exhibited suppressed yet persistent degradation. This demonstrates that degradation behavior can be systematically controlled by cross-linking density. This work provides a molecular design strategy for constructing cellulose-based polymer networks that balance mechanical performance, recyclability, and controlled end-of-life behavior.