Weakening fibril–fibril interactions via an on-demand regulation of hemicellulose phase towards the facile disassembly of lignocellulose heterostructure into approaching native-state elementary fibrils

Abstract

It is of great technical interest but still challenging to develop a cost-effective and eco-friendly method to extract high-aspect-ratio elementary nanofibrils with native-state microstructure from recalcitrant lignocellulosic biomass because established chemical/biological/mechanical approaches inevitably give rise to the breakage of cellulose chains during the nanofibrillation of lignocellulose. Nature has designed hierarchical and heterogeneous lignocellulose structures, among which hemicellulose significantly affects interfibrillar interactions due to its unique molecular structure and micro-distribution pattern. Inspired by this fact, we amplify the hemicellulose stimulation effect on nanofibrillation using an on-demand regulated ionic liquid/water cosolvent and dissociate ultrahigh aspect ratio (2213) elementary fibrils (diameter = 4.7 nm) comprising approaching native-state structural carbohydrates from mildly delignified lignocellulose fibers (i.e. holocellulose) by a low-energy blender. We elucidated the mechanism for the exceptional disassembly behavior of holocellulose fibers: the high-level swelling of the amorphous and negatively charged hemicellulose phase weakens fibril–fibril interactions. The high-aspect-ratio morphology, well-preserved cellulose molecular structure, and hemicellulose-rich surface chemistry of the as-prepared nanofibrils significantly affect their self-assembly behavior and contribute to the extraordinary mechanical and optical performances of the corresponding nanopaper that conventional cellulose nano-papers/composites retain unsurpassed, e.g., overcome general conflicts between strength (310 MPa) and toughness (53 MJ m⁻³) and between transparency (86%) and haze (77%). This work provides a scale-up, ecologically and economically efficient lignocellulose nanostructure-engineered strategy for manufacturing high-performance structural nanomaterials towards a high-tech and carbon-neutral future.