In-situ microstructure regulation towards feasible production of self-reinforced lignocellulose nanopaper with multifunctionality

Lignocellulose is an all-natural structural material with huge potential for a wide range of applications. Extensive studies have designed high-strength LNP via tuning the size/surface chemistry of lignocellulose fibrils for generating sufficient interfacial hydrogen bonds during their self-assembly process. Herein, we demonstrate the fabrication of highly strong LNP via in-situ fibrillation and subsequent self-densification of constituent fibrils induced by a continuous processing of deep eutectic solvent treatment and air-drying. This in-situ microstructure regulation strategy allows the formation of reinforced interfacial hydrogen bonds within LNP, which reveals a combination of high dry and wet strength (188 and 45 MPa, respectively). Moreover, the self-reinforced LNP exhibits intriguing light-management capacity including high visible-light transmittance (92%), considerable transmittance haze (71%) and excellent UV-shielding performance. Outstanding flame retardancy (LOI: 38%) is noted for self-reinforced LNPs arising from its favorable microstructural characteristics such as abundant sulfate groups, high lignin content and densified structure. Intriguingly, the estimated production cost for self-reinforced LNP was approximately one in ten of that for conventional cellulose nanopaper, ascribing from its significantly lower input of resources including materials, water, and energy. Overall, this work innovatively develops an in-situ engineering strategy for economically preparing mechanically strong and multifunctional LNP, which is extremely promising for structural applications.