Solubility of small molecule in ionic liquids: a model study on the ionic size effect

Area of Science:

• Physical Chemistry
• Materials Science
• Chemical Engineering

Background:

• The solvent power of ionic liquids (ILs) was previously modeled using Flory-Huggins (FH) theory, assuming equal component volumes.
• This assumption limits the accurate prediction of solvent properties for diverse ILs.

Purpose of the Study:

• To extend the Flory-Huggins theory to account for differing molar volumes of ionic liquid components.
• To investigate the impact of ionic size on the solvent power of ionic liquids using a polymer-like model.

Main Methods:

• Development of an extended Flory-Huggins theory incorporating a polymer-like model.
• Introduction of effective volumes (V+ and V-) for ionic sites to characterize size effects.
• Comparison of theoretical predictions with experimental solubility data.

Main Results:

• The extended FH theory successfully models solvent power considering varying ionic sizes.
• Effective ionic volume is identified as a key parameter influencing solvent power.
• Larger effective volumes correlate with enhanced solvent power in equivalent ionic liquids.

Conclusions:

• The polymer-like model provides a more accurate description of ionic liquid solvent power.
• Ionic size significantly impacts solvent power, a factor crucial for IL selection.
• The findings offer a theoretical basis for predicting and optimizing ILs for specific applications.