Polarization Effects on the Cellulose Dissolution in Ionic Liquids: Molecular Dynamics Simulations with Polarization...

Area of Science:

• Polymer Science
• Computational Chemistry
• Materials Science

Background:

• Cellulose, a biopolymer, exhibits limited solubility in common solvents.
• Ionic liquids offer potential as novel solvents for cellulose dissolution and processing.
• Understanding cellulose conformation and interactions in ionic liquids is crucial for its applications.

Purpose of the Study:

• To investigate the conformational changes of cellulose oligomers in 1,3-dimethylimidazolium chloride ([C1mim]Cl).
• To analyze the intermolecular interactions between cellulose and the ionic liquid components.
• To explore the role of force field models and enhanced sampling in simulating cellulose behavior.

Main Methods:

• Molecular dynamics (MD) simulations using fixed-charge and polarizable force fields.
• Integrated tempering enhanced sampling method for improved sampling efficiency.
• Infrared spectroscopy for experimental validation of interactions.

Main Results:

• Cellulose transitions from a helical to a flexible conformation in [C1mim]Cl.
• Pyranose rings primarily adopt a chair conformation, with boat/skew-boat forms appearing at higher polymerization degrees.
• Chloride anions form strong hydrogen bonds with cellulose hydroxyl groups, indicating favorable interactions.
• Electrostatic interactions dominate over van der Waals forces; anion interactions are stronger than cation interactions.

Conclusions:

• The ionic liquid [C1mim]Cl effectively alters cellulose conformation and promotes dissolution through strong anion interactions.
• Polarizable force fields and enhanced sampling methods provide a more comprehensive understanding of cellulose behavior.
• The findings support the use of specific ionic liquids for cellulose processing and suggest limitations for aqueous dissolution.