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

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.