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A Surfactant-Free Middle-Phase Microemulsion System Formed by n-Hexadecane, n-Butanol, and Water
Wenchao Ma1, Na Du1, Wanguo Hou1
1Key Laboratory of Colloid & Interface Chemistry (Ministry of Education), Shandong University, Jinan 250100, P. R. China.
Langmuir : the ACS Journal of Surfaces and Colloids
|June 9, 2026
Summary
Surfactant-free microemulsions (SFMEs) can form middle-phase microemulsions, similar to traditional systems. This study investigates SFME phase behavior and structure, confirming Winsor III formation without surfactants.
Area of Science:
- Colloid and Surface Science
- Materials Science
- Physical Chemistry
Background:
- Surfactant-free microemulsions (SFMEs) utilize amphi-solvents instead of traditional surfactants.
- Understanding SFMEs is limited, particularly regarding their ability to form middle-phase (Winsor III) systems.
Purpose of the Study:
- To investigate the phase behavior of a ternary mixture of n-hexadecane, n-butanol, and water.
- To determine if surfactant-free systems can form middle-phase microemulsions (Winsor III).
Main Methods:
- Phase behavior analysis of the ternary mixture at varying temperatures (20-90 °C).
- Dynamic light scattering, electrical conductivity measurements.
- Cryogenic and negative-staining transmission electron microscopy for mesoscale structure determination.
Main Results:
- Observed single-phase, two-phase, and three-phase patterns depending on composition.
- The three-phase region decreased with increasing temperature (20-55 °C).
- Identified the middle phase as a bicontinuous (BC) microemulsion, confirming Winsor III formation without surfactants. Also identified Winsor I, II, and IV systems.
Conclusions:
- Demonstrates that middle-phase (Winsor III) microemulsions can be formed without traditional surfactants.
- Provides a deeper understanding of the characteristics and phase behavior of surfactant-free microemulsions.
- Highlights the potential of amphi-solvent systems in microemulsion formation.
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