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Phase Inversion of Pickering Emulsions Induced by Interfacial Electrostatic Attraction
Guanqing Sun1, Tiehuang Guo1, Jing Luo1
1Key Laboratory of Synthetic and Biological Colloids, Ministry of Education, School of Chemical and Material Engineering, Jiangnan University, Wuxi, Jiangsu 214122, China.
Langmuir : the ACS Journal of Surfaces and Colloids
|January 12, 2023
Summary
Researchers achieved phase inversion of Pickering emulsions from water-in-oil to oil-in-water by creating an interfacial particle bilayer. This method utilizes electrostatic attraction between oppositely charged particles, offering tunable emulsion stability.
Area of Science:
- Colloid and Surface Science
- Materials Science
- Physical Chemistry
Background:
- Pickering emulsions are stabilized by solid particles at the oil-water interface.
- Phase inversion is a critical process for tailoring emulsion properties.
- Controlling emulsion type (W/O vs. O/W) is essential for various applications.
Purpose of the Study:
- To achieve phase inversion of Pickering emulsions from water-in-oil (W/O) to oil-in-water (O/W).
- To investigate the mechanism of phase inversion using oppositely charged particles.
- To demonstrate tunable emulsion stability through particle design.
Main Methods:
- Emulsification using cationic silica-FITC particles in toluene to stabilize W/O emulsions.
- Induction of phase inversion by adding anionic silica-RB particles to the aqueous phase.
- Analysis of particle size, surface charge, pH, and salt concentration effects.
- Characterization using Confocal Laser Scanning Microscopy (CLSM) and Scanning Electron Microscopy (SEM).
- Evaluation of emulsion stability via osmotic pressure measurements and centrifugation.
Main Results:
- Cationic silica particles (600 nm) stabilized W/O emulsions in toluene.
- Addition of anionic silica-RB particles (1.0 wt % or higher) induced phase inversion.
- Smaller anionic silica-RB particles (100 nm) induced inversion at lower concentrations (0.4 wt %).
- Interfacial particle bilayers were visualized using CLSM and SEM.
- Electrostatic attraction mechanism confirmed by tuning surface charge density.
- Emulsion stability was successfully tuned.
Conclusions:
- Phase inversion of Pickering emulsions can be achieved by forming an interfacial particle bilayer via electrostatic attraction.
- The size and surface charge density of particles are key parameters for controlling phase inversion and emulsion stability.
- This study provides a mechanism for tunable Pickering emulsion stabilization.
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