Ionic Liquid Character of Zinc Chloride Hydrates Define Solvent Characteristics that Afford the Solubility of Cellulose

Abstract

The recently described ionic liquid structure of the three equivalent hydrate of zinc chloride (ZnCl2·R H2O, R = 3, existing as [Zn(OH2)6][ZnCl4]) explains the solubility of cellulose in this medium. Only hydrate compositions in the narrow range of 3 - x < R < 3 + x with x ≈ 1 dissolve cellulose. Once dissolved, the cellulose remains in solution up to the R = 9 hydrate. Neutron diffraction and differential pair distribution function analysis of cellulose and model compound solutions (1 wt % cellulose in the R = 3 hydrate and 1 wt % ethanol in the R = 3 hydrate and the ZnCl2·3 ethanol liquid) coupled with detailed solubility measurements suggest that cellulose solubility occurs via coordination of the primary OH to the hydrated zinc cation with ring hydroxyls forming part of a second coordination shell around the cation of the ionic liquid.

Acid‐Catalyzed Conversion of Carbohydrates into Value‐Added Small Molecules in Aqueous Media and Ionic Liquids

“…However, only ZnCl 2 ⋅ n H 2 O ( n= 3–4) has presently found an application in the chemical conversion of this polysaccharide into platform molecules . ZnCl 2 ⋅ n H 2 O is considered to be an IL, possessing the formula [Zn(OH 2 ) 6 ][ZnCl 4 ] in the case of n= 3 . The high dissolving power of such ILs might be attributed to the coordination and strong interaction between the hydroxyl groups of the solvent and polymer .…”

“…[173][174][175] ZnCl 2 ·n H 2 Oi s considered to be an IL, possessing the formula [Zn(OH 2 ) 6 ] [ZnCl 4 ]i nt he case of n = 3. [176,177] The high dissolving power of such ILs might be attributedt othe coordination and strong interaction between the hydroxyl groups of the solventa nd polymer. [177] These solvent-substrate interactions may lead to the specific pathways in the transformation of cellulose described below.…”

Self‐Assembled Polymeric Ionic Liquid‐Functionalized Cellulose Nano‐crystals: Constructing 3D Ion‐conducting Channels Within Ionic Liquid‐based Composite Polymer Electrolytes

“…On the other hand, for the IL(LiTFSI)/PIL electrolyte with a5wt.% PIL content,asignificant decrease in ionic conductivity (3.5-16.5 mS cm À1 at 30-100 8C) was observed as compared to the introduced PIL-fOCNC IL(LiTFSI) with same solid content.F rom the above observations,w es peculate that the added PIL-fOCNC interacts with the ILs, through specific interactions, to enhancet he dissociation of IL, thereby resulting in an increase in the number of ion carriers and ionic diffusivity in the electrolytes. [12,25] As mentioned above, OCNC-basedC CPE can be obtained by casting the PY 14 (LiTFSI)/PIL-fOCNC mixture with 40 wt.%o f IL(LiTFSI) from as olution of av olatile MeCN;t he resulting solid film has sufficient physical strength to maintain af ilm shape. It is noteworthy that the plain PY 14 (LiTFSI)/PIL did not give af ilm with the same form as IL(LiTFSI) loading (the maximum loading 30 wt.%), indicating that the higher capacity of IL(LiTFSI) in IL(LiTFSI)/PIL-fOCNCC CPE results from its unique network structure.…”

Inorganic Salts Induce Thermally Reversible and Anti‐Freezing Cellulose Hydrogels

“…[12] Subsequent addition of calcium ions to the system connects the adjacent Zn-cellulose junction zones through cooperative interactions. Cotton cellulose was used as the starting material.…”

“…Particularly,the ZnCl 2 hydrate exists in the form of the ionic liquid ([Zn(OH 2 ) 6 ][ZnCl 4 ], which has extraordinary hydrogen-bond-donating ability.T he zinc species competes with the protons for the hydroxyl groups in the cellulose chains.The intrinsic hydrogen-bonding networks are weakened and the cellulose chains become flexible.W ater molecules penetrate into the cellulose sheets and lead to cellulose solubility. [12] Subsequent addition of calcium ions to the system connects the adjacent Zn-cellulose junction zones through cooperative interactions. [13] Zn 2+ ions contribute to the cellulose dissolution and Ca 2+ ions act as ag elling agent.…”