Phase Inversion and Interfacial Layer Microstructure in Emulsions Stabilized by Glycosurfactant Mixtures

Area of Science:

• Colloid and Surface Science
• Materials Science
• Physical Chemistry

Background:

• Emulsion kinetic stability is crucial for various scientific and technological applications.
• Controlling emulsion stability often relies on understanding surfactant behavior at interfaces.

Purpose of the Study:

• To investigate the relationship between emulsion stability and the supramolecular organization of surfactants at the oil-water interface.
• To explore how different oil types (linear vs. branched) and surfactant mixtures (Span80 and Tween80) influence emulsion structure and stability.

Main Methods:

• Construction of pseudo-phase diagrams for emulsions.
• Analysis of surfactant ordering and dynamics using electron paramagnetic resonance (EPR) spectroscopy.
• Monitoring emulsion stability and phase inversion using conductometry.

Main Results:

• Stable oil-in-water (O/W) emulsions ( > 4 days) exhibited disordered surfactant tails forming a compact, viscous layer.
• Less stable water-in-oil (W/O) emulsions showed ordered surfactant tails extending into the oil phase.
• A gradual change in surfactant layer microstructure occurred during phase inversion, contrasting with abrupt changes observed via conductometry.

Conclusions:

• Emulsion stability is directly linked to the microstructuring of the surfactant layer at the oil-water interface.
• The findings provide insights for the rational design of stable emulsions by controlling surfactant organization.
• Understanding surfactant supramolecular organization is essential for tailoring emulsion properties.