Insight into the Cosolvent Effect of Cellulose Dissolutionin Imidazolium-Based Ionic Liquid Systems.

Recently,it has been reported that addition of a cosolvent significantlyinfluences solubility of cellulose in ionic liquids (ILs), but littleis known about the influence mechanism of the cosolvent on the molecularlevel. In this work, four kinds of typical molecular solvents (dimethylsulfoxide (DMSO), N,N-dimethylformamide(DMF), CH3OH, and H2O) were used to investigatethe effect of cosolvents on cellulose dissolution in [C4mim][CH3COO] by molecular dynamics simulations and quantumchemistry calculations. It was found that dissolution of cellulosein IL/cosolvent systems is mainly determined by the hydrogen bondinteractions between [CH3COO]−anionsand the hydroxyl protons of cellulose. The effect of cosolvents onthe solubility of cellulose is indirectly achieved by influencingsuch hydrogen bond interactions. The strong preferential solvationof [CH3COO]−by the protic solvents (CH3OH and H2O) can compete with the cellulose–[CH3COO]−interaction in the dissolution process,resulting in decreased cellulose solubility. On the other hand, theaprotic solvents (DMSO and DMF) can partially break down the ionicassociation of [C4mim][CH3COO] by solvationof the cation and anion, but no preferential solvation was observed.The dissociated [CH3COO]−would readilyinteract with cellulose to improve the dissolution of cellulose. Furthermore,the effect of the aprotic solvent-to-IL molar ratio on the dissolutionof cellulose in [C4mim][CH3COO]/DMSO systemswas investigated, and a possible mechanism is proposed. These simulationresults provide insight into how a cosolvent affects the dissolutionof cellulose in ILs and may motivate further experimental studiesin related fields. [ABSTRACT FROM AUTHOR]