Dissolution and regeneration behavior of cellulose in a choline hydroxide/urea/zinc glycinate ternary deep eutectic solvent

In this study, a series of ternary deep eutectic solvent systems composed of choline hydroxide (ChOH), urea (Ur), and zinc salt compounds (ZSCs) were synthesized and utilized to investigate the dissolution and regeneration performance of cellulose. The results indicated that the DES system composed of ChOH, Ur, and zinc glycinate (ZG) exhibited excellent cellulose dissolution capabilities. OH⁻ in this system attacks the hydroxyl groups of cellulose, while glycine anions may form hydrogen bonds with cellulose hydroxyl groups. Meanwhile, urea and Zn²⁺ may stabilize the solution and prevent cellulose self-aggregation, thus facilitating its dissolution. Water content of 3.85 wt% ChOH/Ur/ZG showed the best cellulose dissolution at 65 °C, able to dissolve 12 wt% of microcrystalline cellulose with a degree of polymerization of 152 and confirmed the system's suitability for a wide DP by dissolving a wide range of feedstocks. The crystalline form of regenerated cellulose is typical of type II cellulose, with good thermal stability and low consumption of crystallinity and polymerization during dissolution. Notably, ChOH/Ur/ZG also showed excellent reusability, maintaining more than 80 % cellulose solubilization efficiency after three cycles. ChOH/Ur/ZG broadens the versatility of cellulose solvent systems and opens up new avenues for the preparation of regenerated cellulosic functional materials.