Understanding the interactions of cellulose with ionic liquids: a molecular dynamics study

Area of Science:

• Biomass Conversion
• Materials Science
• Computational Chemistry

Background:

• Ionic liquids (ILs) are effective solvents for cellulose and lignocellulosic biomass.
• A clear rationale for selecting ILs for biopolymer dissolution is lacking.

Purpose of the Study:

• Develop an all-atom force field for 1-ethyl-3-methylimidazolium acetate ([C2mim][OAc]).
• Investigate cellulose behavior in [C2mim][OAc] using molecular dynamics (MD) simulations.
• Compare cellulose interactions in [C2mim][OAc] with water and methanol.

Main Methods:

• Developed an all-atom force field for [C2mim][OAc].
• Performed MD simulations on beta-d-glucose oligomers (n=5-20) in [C2mim][OAc], water, and methanol.
• Calculated thermodynamic properties and solute-solvent interaction energies.

Main Results:

• Interaction energy between cellulose and [C2mim][OAc] was greater than with water or methanol.
• Acetate anions formed hydrogen bonds with cellulose hydroxyl groups.
• Cations exhibited hydrophobic interactions with cellulose, suggesting a significant role in dissolution.
• Cellulose conformation changed in [C2mim][OAc] compared to crystalline cellulose in water.

Conclusions:

• The cation in [C2mim][OAc] significantly contributes to cellulose dissolution.
• This study provides the first theoretical insights into key factors for cellulose dissolution by ionic liquids.