Choline hydroxide based deep eutectic solvent for dissolving cellulose

Abstract

New cellulose solvent based on choline hydroxide/urea (ChOH/Ur) deep eutectic solvent (DES) was developed. The ChOH/Ur DES has a promising solubility for cellulose compared to ChCl-based DESs. ChOH/Ur DES with ca. 11 wt% water can dissolve at least 9.5 wt% cellulose with the degree of polymerization (DP) of 926 within 30 min. Compared to the ionic liquids, the temperature window of ChOH/Ur is wide and close to room temperature. The ChOH/Ur DES also showed more tolerance to water than ionic liquid, which can save energy in preparation and usage. The physical and chemical properties of DES and cellulose solution were investigated. The ChOH/Ur DES system is a non-derivatizing solvent for cellulose. The preliminary rheological results suggest that the dynamics of cellulose solution in ChOH/Ur system is similar to that of salt-free polyelectrolyte solutions. The degradation of cellulose during the dissolution and storage of the cellulose solution is limited. After 7 days of storage at 40 °C, the DP of the regenerated cellulose remained at about 80% of the raw material. The ChOH/Ur is recyclable without the loss of solubility of cellulose. In conclusion, the ChOH/Ur DES system is a promising green solvent platform for preparing regenerated cellulose materials and could be used as a media for cellulose chemistry.