Effect of Protic and Aprotic Solvents on the Mechanism of Cellulose Dissolution in Ionic Liquids: A Combined Molecular Dynamics and Experimental Insight

Abstract

The present study is undertaken to reveal the effect of cosolvents on the dissolution behaviour of cellulose in 1‐ethyl‐3‐methylimidazolium acetate ([Emim][OAc]) by both quantum chemical (QC) and Molecular Dynamic (MD) simulations. Two categories of cosolvents namely protic and aprotic solvents have been selected in order to enhance the cellulose dissolution in ionic liquid (IL). In the typical IL/cosolvent system, anion of the IL was found to be strongly solvated by the protic solvents (Formamide and Acetamide) thereby resulting in decreasing cellulose solubility, whereas it gave contrary trend for aprotic solvents (DMSO, DMF, DMAc). The dissolution of cellulose was essentially quantified by the cellulose‐anion interactions by studying the non‐bonded interaction energies. Furthermore, the solid‐liquid equilibria experiments were conducted for cellulose in IL and IL/cosolvent mixtures to confirm the simulated results. From MD simulations and experimental results, DMSO was found to be the best cosolvent for the enhancement of cellulose dissolution in IL. The regenerated cellulose was then characterized by Fourier transform spectroscopy (FTIR), X‐ray diffraction (XRD) and thermal gravimetric analysis (TGA). From the TGA analysis, thermal stability of regenerated cellulose was found to be reduced by 6 °C at room temperature.

Glycerin/NaOH Aqueous Solution as a Green Solvent System for Dissolution of Cellulose

“…The transition of CH 2 around 1427 cm −1 (in pristine cellulose) to CH around 1369 cm −1 (in regenerated cellulose) after regenerating indicates the rotational isomer variation from C3-O3 and C6-O6. This further convinces the transition from cellulose I to cellulose II [34]. The absorption peak around 893 cm −1 is the outward stretching vibration of asymmetric rings which corresponds to the vibration band of C5 and C6.…”

“…The transition of CH 2 around 1427 cm −1 (in pristine cellulose) to CH around 1369 cm −1 (in regenerated cellulose) after regenerating indicates the rotational isomer variation from C3–O3 and C6–O6. This further convinces the transition from cellulose Ⅰ to cellulose II [ 34 ].…”

Phase transition properties, chemical purity, and solubility of coniferyl alcohol and D‐mannose: Experimental and Cosmo‐RS predictions

“…After the successful determination of the phase transition properties of coniferyl alcohol and D‐mannose by DSC, the solubility of both the coniferyl alcohol and D‐mannose was predicted in ionic liquids (ILs) using the COSMO‐RS model. In this section, we have chosen the novel ILs as solvents since they have proved to be effective solvents for biomass dissolution . For improved solubility, the ions of the IL should obey the following criteria: (a) one of the ions should be highly polar and act as a good hydrogen bond acceptor or donor; and (b) the other IL ion should be slightly polar .…”

Recent Advances in Solvents for the Dissolution, Shaping and Derivatization of Cellulose: Quaternary Ammonium Electrolytes and their Solutions in Water and Molecular Solvents

“…Each negative chain is most certainly surrounded by a sheath of the TBA + cation. The synergism between electrostatic repulsion of Cel-OH···anion, and steric repulsion of Cel-OH···anion/cation complexes appear to prevent association between cellulose chains and favor a molecularly dissolved state as shown for QAEs [ 83 ], and, e.g., for the ILs BuMeIm [ 26 , 84 , 98 , 99 , 100 , 101 , 102 , 103 ] or EtMeIm cation [ 104 , 105 , 106 , 107 , 108 ].…”