(702e) Solvation and Thermodynamics of Cellulose In Water and Ionic Liquid

hindered by cellulose recalcitrance.  Recently, it was found that certain classes of ionic 

liquids (ILs) can dissolve cellulose into its constituent glucan chains.  To understand the 

molecular forces provided by ILs to break down crystalline cellulose, we performed all- 

atom molecular dynamics (MD) simulations of two extreme states of cellulose: a 

crystalline microfibril and a dissociated state in which all the glucan chains of the 

crystalline microfibril are fully detached from each other. MD simulations of the two 

states are performed in water and in the IL 1-butyl-3-methylimidazolium chloride 

(BmimCl) to provide a comprehensive analysis of solvent effects on cellulose dissolution. 

The results highlight two unprecedented insights in the dissolution of cellulose by 

solvent-mediated interactions. First, the perturbation of solvent structures by dissolved 

glucan chains can be a dominant factor in determining solubility. We show that the 

insolubility of cellulose in water at 300 K arises mostly from reduction in solvent 

entropy. Second, for BmimCl, the driving force for cellulose dissolution comes from 

energetics, and more importantly, that both the Cl- and the Bmim+ ions can exert 

disruptive effects on C-H---O intersheet interactions, which we show to be the most 

significant molecular source of cellulose recalcitrance. Cl- anions are observed to form 

hydrogen bonds (HBs) with the hydroxyl groups of glucan chains from either the 

equatorial or axial directions, thereby disrupting intersheet connections. Bmim+ cations 

are observed directly interacting with glucan chains along the axial directions. Therefore, 

the ability of BmimCl to interact favorably with not just the OH groups of cellulose, but 

also the CH groups of cellulose is what enables it to disrupt the entirety of cellulose’s 

internal interaction network and makes it an effective cellulose solvent.