Tailoring lignocellulosic nanofibrils via controlled delignification for high reinforcing capacity in poly(butylene...

Motivated by the pursuit of minimal processing routes to obtain highly fibrillated nanocellulose for reinforcing biodegradable polymers, in this work we engineered lignin-containing cellulose nanofibrils (LCNFs) for optimal interfacial compatibility with poly(butylene adipate-co-terephthalate) (PBAT) on the preparation of nanocomposites films via casting. Lignin contents (from 3 to 15 wt%) were adjusted within nanofibrils from sugarcane bagasse via alkaline treatment and mechanical fibrillation, producing LCNFs with diameter ranging from 4 to 5 nm. The residual lignin at nanofibers functioned as a toolbox to tailor its surface energy and assess their effects on mechanical performance and active properties of the nanocomposites, such as enhanced hydrophobicity and UV-shielding capability. Transmission Electron Microscopy images showed that residual lignin dictates the distribution of the LCNF within PBAT, modulating stress dissipation in the material. Spectroscopic analysis (Attenuated Total Reflectance-Fourier Transform Infrared and X-ray Photoelectron Spectroscopies) indicated that the aromatic moieties from lignin on the surface of the nanofibrils promoted supramolecular interactions with PBAT chains, improving the mechanical performance of the latter. The nanocomposite containing only 3 wt% LCNF with 11 wt% of lignin reached a 68% increase in elastic modulus compared to neat PBAT, outperforming commonly reported CNF-PBAT systems. Here, we highlight the great capabilities of minimally processed cellulose nanofibrils as a high-performance reinforcer in polymeric nanocomposites. Our residual lignin-centered compatibilization strategy utilizes the inherent synergy among biomass components for higher performance of nanocomposite.