The Influence of Water on Choline-Based Ionic Liquids

Area of Science:

• Biomedical Engineering
• Materials Science
• Physical Chemistry

Background:

• Choline and geranic acid (CAGE)-based ionic liquids are emerging for drug delivery.
• Understanding CAGE behavior in aqueous environments is crucial for biomedical applications.
• Water significantly alters ionic liquid physicochemical properties.

Purpose of the Study:

• To investigate the microscopic structure and properties of CAGE with varying water content.
• To determine the impact of water on CAGE stability and interactions.
• To assess the suitability of CAGE for drug delivery in physiological conditions.

Main Methods:

• Equimolar CAGE (1:1 choline/geranic acid) was studied.
• Viscosity, conductivity, and self-diffusion coefficients were experimentally measured.
• Computational characterization was employed to analyze microscopic structures.

Main Results:

• Stored 1:1 CAGE contained up to 0.20 mole fraction water.
• Intraionic interactions remained largely unchanged until water exceeded 0.65 mole fraction.
• Geranate ion reorganization and increased anion tail interactions were observed above 0.65 mole fraction water, evidenced by a viscosity plateau.

Conclusions:

• CAGE demonstrates stability in the presence of moderate water content (up to 0.65 mole fraction).
• The findings suggest CAGE can be used in drug delivery applications without predrying.
• Dilution can be used to control anion organization for tailored applications.