Controllable preparation of nano-cellulose via natural deep eutectic solvents prepared with lactate and choline chloride

Pretreatment with deep eutectic solvent is highly desirable to improve the efficiency of the preparation of nano-cellulose and simplify the operation. The natural deep eutectic solvent (NADES) composed of lactate (LA) and choline chloride (CC) was applied for the preparation of nano-cellulose under mild conditions accompanied by simultaneous esterification modifications of it. The effects of the treatment conditions on the structure and properties of nano-cellulose were investigated and explained the mechanism from the perspective of molecular simulation. The results showed that the reaction time of nano-cellulose could be shortened to 3 h, and the reaction temperature could be as low as 100 °C. The esterification of cellulose not only avoided over-hydrolysis and dissolution in the pretreatment process but also ensured the high yield of nano-cellulose (up to 75 %−89 %). The crystallinity of nano-cellulose decreased compared with the raw material due to the influence of mechanical action. The nano-cellulose fibers (NCF) and nano-cellulose crystals (NCC) with different lengths were achieved by controlling the reaction conditions of the pretreatment of NADES. The esterification modifications of NADES on cellulose during the dissolution of nano-cellulose were confirmed by molecular simulation. The nano-cellulose prepared by this system has good stability, biocompatibility, and degradability, which can be used in the fields of medicine, strengthening composite materials, and emulsion emulsifiers.