Self-exfoliation of cellulose nanofibrils via one-pot pseudosolvent swelling/esterification for functional pellicular materials.

Nanocellulose, an environmentally friendly and biodegradable high-performance material, holds significant promise for diverse applications. However, its widespread commercialization is severely hindered by its high energy-intensive and low-yield production processes. Here, we present a facile method for preparing cellulose nanofibrils (CNFs) through a self-exfoliation approach using a pseudosolvent. The pseudosolvent selectively disrupted the hydrogen bonds between elementary nanofibers without causing dissolution, enhancing the reactivity of surface hydroxyl groups for subsequent modifications. By incorporating ionizable esterification groups, a rapid and low-energy self-exfoliation of CNFs was achieved. The resulting CNFs exhibited nano-size dimensions, with 440-780 nm lengths and 2.2-4.5 nm thicknesses. The CNF dispersions exhibited pH responsive behavior, enabling a controlled demulsification and facile recovery of Pickering emulsions by varying pH. Furthermore, the CNF nanomembranes displayed vibrant rainbow colors under natural light. Macroscopic membrane demonstrated a high Young's modulus of 3.8 GPa, breaking strength of 95.9 MPa, transmittance over 80 %, and haze over 90 %. Ethanol soaking endowed the films with programmable shape memory and erasable properties, paving the way for advancements in nanocellulose preparation, surface modification, and applications.