Deep eutectic solvent to obtain hydrophobic nanocellulose in a single step

Abstract

This work presents a versatile, efficient and more sustainable process to obtain acetylated hydrophobic nanocellulose (AcNC) in a single step using a ternary eutectic system (ChCl/pTSA/PA, 1:1:1.35) as a solvent and catalyst, and acetic anhydride as an acetylating agent. This method replaces conventional toxic and corrosive solvents, such as strong acids with a recyclable and non-volatile medium. The optimal conditions (80 degrees C, 3 h, 3 mL of Ac2O) yielded AcNC with a degree of substitution (DS) of 2.4, enhanced hydrophobicity measured by a water contact angle (WCA) of 64.2 degrees, and superior thermal stability (Tmax of 379 degrees C). At the laboratory scale, the process achieved yields of 61-77% while maintaining the nanometric properties of the material, even when scaled up volume DES to 1000 mL. Furthermore, the ternary solvent was successfully reused for five cycles without significant efficiency loss, underscoring its economic and environmental viability. This method offers a promising alternative to produce functionalized nanocellulose with potential applications in advanced materials and sustainable coatings.