Hydrogen-Bond Network Modulation of Cellulose Nanocrystal Films by Sodium Lipoate for Closed-Loop Recycling

Developing redispersible nanocellulose products is crucial for their industrial applications. However, challenges persist in developing convenient and efficient processes. This study presents a green strategy using dynamic covalent chemistry to tune the hydrogen-bonding network of cellulose nanocrystals (CNCs). CNCs were combined with sodium lipoate (SL) in an aqueous solution and dried to form composite films. SL incorporation effectively prevents CNC aggregation via electrostatic repulsion and steric hindrance, transforming the CNC skeleton structure from a "bundle-to-bundle" structure to a uniform, horizontally stacked architecture. The composite films exhibited enhanced transparency, surface smoothness, and tunable mechanical properties. Upon water immersion, SL depolymerized and separated with 100% recovery. The remaining CNC skeleton readily redispersed into individual nanocrystals via sonication, achieving near-complete recovery even with 15% SL. This simple, water-based process tailors CNC film performance and enables complete closed-loop recycling, offering sustainability and simplicity for advanced applications.