Ionic Liquid-Based Microemulsions with Reversible Microstructures Regulated by CO₂

Area of Science:

• Materials Science
• Chemical Engineering
• Physical Chemistry

Background:

• Amine-based microemulsions are prone to volatilization, posing environmental and efficiency challenges.
• Ionic liquids offer tunable properties but their application in responsive systems requires further exploration.
• Controlling microemulsion microstructure is key for applications in separation and delivery.

Purpose of the Study:

• To design and synthesize CO2-responsive microemulsions utilizing a novel ionic liquid surfactant.
• To investigate the ability of these microemulsions to reduce amine volatilization.
• To explore the reversible microstructural transitions induced by CO2 and N2/heat.

Main Methods:

• Synthesis of 1,1,3,3-tetramethylguanidine-oleic acid (TMG-OA) ionic liquid.
• Characterization of TMG-OA properties using NMR, pH, thermogravimetry, and interfacial tension measurements.
• Preparation and characterization of CO2-responsive microemulsions with varying isopropyl alcohol (IPA) content.

Main Results:

• TMG-OA demonstrated excellent switchability, stability, and surface activity.
• Microemulsion size increased with CO2 introduction and decreased with N2/heat for higher IPA content.
• Phase separation and regeneration of microemulsions with different sizes were observed for lower IPA content upon CO2/N2 cycling.

Conclusions:

• The developed TMG-OA ionic liquid is effective in creating CO2-responsive microemulsions.
• These microemulsions offer a promising approach to mitigate amine volatilization.
• Reversible microstructural changes are driven by the CO2-induced conversion between TMG-OA and oleic acid components.