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Ren, H., Chen, C., Wang, Q., Zhao, D., and Guo, S. (2016). "The properties of choline chloride-based deep eutectic solvents and their performance in the dissolution of cellulose," BioRes. 11(2), 5435-5451.

Abstract

A series of choline chloride-based deep eutectic solvents (ChCl-DESs) were synthesized and characterized, and their performance in the dissolution of cellulose was investigated. The hydrogen-bond donors significantly (β-value) affected the properties of ChCl-DESs, causing differentiated dissolution performances. ChCl- imidazole (Im) showed the highest Hammett acidity function (1.869), hydrogen bond basicity (0.864), and dipolarity/polarizability effect (0.382) among the ChCl-DESs. The ChCl-Im showed the lowest pseudo-activation energy for viscous flow (31.76 kJ mol-1) among the ChCl-DESs. The properties of ChCl-Im caused the highest solubility of cellulose (2.48 wt.%) relative to the other ChCl-DESs. Polyethylene glycol (PEG), as a co-solvent, significantly (β-value) enhanced the accessibility of ChCl-Im to cellulose by breaking the supramolecular structure of cellulose, promoting its dissolution. The decrystallization of ChCl-Im-coupled PEG approximately doubled the dissolving capabilities, and the solubility increased by more than 80% in comparison with only ChCl-Im. The cellulose was directly dissolved by ChCl-Im-coupled PEG, and no other derivatives were produced.
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