Methodology of Redispersible Dry Cellulose Nanofibrils Powder Synthesis under Waterless Condition

Cellulose nanofibrils (CNFs) are environmentally friendly and biocompatible nanomaterials with good mechanical properties, which are of great importance for producing the next-generation materials. However, common methods used for preparing CNFs are water dependent and challenging in CNFs separation, morphology control, antibacterial preservation, and delivery. Herein, a waterless and environmentally benign protocol with high product yield is explored for the synthesis of dry CNFs powder by intergrating liquefaction and homogenization from either wood pulp or cotton resource. Low-toxicity, degradable, and biocompatible citric acid is used instead of sulfuric acid, and the replacement of water by ethylene glycol and ethanol can be successfully achieved. The measured diameter and length of CNFs are around 50 nm and no less than 300 nm, respectively. Compared to the properties of the raw materials, the slight change in the crystallinity of CNFs does not affect its thermal stability. As additional advantages of the current method, the CNFs are very easy to be stored, delivered, and redispersed in water, and the solvent can be easily separated and recycled. This work will bring feasibility and facility of large-scale synthesis of CNFs under anhydrous conditions.