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Dynamic Partitioning of Surfactants into Nonequilibrium Emulsion Droplets
Rebecca V Balaj1, Wangyang Xue1, Parvin Bayati1
1Department of Chemistry, The Pennsylvania State University, University Park, Pennsylvania 16802, United States.
Journal of the American Chemical Society
|September 10, 2024
Summary
Nonionic surfactants concentrate in shrinking oil droplets under nonequilibrium conditions, forming stable emulsions. This partitioning behavior influences emulsion properties and can be modulated by ionic surfactants.
Area of Science:
- Physical Chemistry
- Colloid and Surface Science
- Materials Science
Background:
- Partitioning behavior is crucial for understanding chemical concentrations in heterogeneous mixtures.
- Equilibrium conditions may not accurately describe out-of-equilibrium systems like oil-in-water emulsions.
- Surfactant partitioning in dissolving oil droplets is key to emulsion stability and properties.
Purpose of the Study:
- Investigate nonequilibrium partitioning of nonionic surfactants between shrinking oil droplets and water.
- Analyze how surfactant composition, concentration, and oil structure affect partitioning.
- Explore the use of ionic surfactants to modulate partitioning and control phase behavior.
Main Methods:
- Quantitative mass spectrometry for analyzing individual microdroplet composition over time.
- Controlled experiments with varying surfactant and oil compositions.
- Utilizing stimuli-responsive ionic surfactants to influence partitioning.
Main Results:
- Nonionic surfactants rapidly partition into oil droplets, reaching high nonequilibrium steady-state concentrations.
- Surfactants are released as droplets solubilize, causing transient interfacial concentrations and microemulsion formation.
- Ionic surfactants reduce nonionic surfactant partitioning; stimuli-responsive ones enable reversible phase control.
Conclusions:
- Nonequilibrium partitioning significantly impacts emulsion properties and stability.
- Understanding these nonequilibrium states is vital for designing and controlling emulsions.
- Stimuli-responsive surfactants offer a pathway for dynamic control of emulsion phases.
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