Toward Overcoming the Strength-Toughness Trade-off in Cellulose Bulk Material by Tuning the Double-Network Structure With Hierarchical Hydrogen Bonding

Overcoming the conflict between strength and toughness in polymer-matrix composites without chemically cross-linked networks remains challenging. Herein, we report an all-cellulose bioplastic (AC-bioplastic) with excellent strength and toughness via a hierarchical hydrogen-bonding double-network (DN) structure. Natural wood fibers are delignified to cellulose microfibers, which cross-link with regenerated cellulose nanofibers formed using LiCl/DMAc solvent, creating an interpenetrating DN network. The strong hydrogen bonds (H-bonds) between micro/nano-cellulose networks provide primary mechanical strength for AC-bioplastic, while the weak H-bonds formed by the interaction between Cl⁻ and cellulose nanofibers contribute to the slipping and deformation behaviors. As a result, the AC-bioplastic exhibits a tensile strength of 95.8 MPa and a toughness of 84.8 MJ m⁻³, surpassing many representative cellulose-based materials while remaining comparable to state-of-the-art polymeric elastomers. Notably, the thickened AC-bioplastic bulk achieves a compression strength of 200 MPa under a high strain rate of 4000 s⁻¹, outperforming typical impact-resistant materials including PC and ABS. Importantly, this approach avoids complete cellulose nanofibril dissociation, enabling the facile and scalable manufacturing. Combined with its intrinsic thermal stability and recyclability, the AC-bioplastic provides a promising lightweight and renewable alternative for sustainable structural materials.