Efficient Cleavage of Strong Hydrogen Bonds in Cotton by Deep Eutectic Solvents and Facile Fabrication of Cellulose Nanocrystals in High Yields

The content of cellulose in biomass is important for producing nanocellulose in high yields. Cotton fibers containing ultrahigh purity (∼95%) cellulose are ideal feedstock for nanocellulose production. However, the presence of strong hydrogen bonding between the cellulose chains limits the use of cotton fibers for the production of nanocellulose in a facile and mild process. Here, efficient cleavage of the strong hydrogen bonds in cotton and ultrafast fabrication of cellulose nanocrystals (CNCs) with a high yield of 74.2% were first realized through a 3 min microwave-assisted deep eutectic solvent pretreatment and a subsequent high-intensity ultrasonication process. The obtained CNCs had diameters of 3–25 nm, and lengths ranged between 100 and 350 nm. The CNCs also displayed a relative crystallinity of 82%, and the thermal degradation temperature started from 320 °C. The study provides a green and efficient method for the mass production of cotton CNCs, and is expected to contribute to improving the refinery utilization of cotton feedstock.