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Ripening of catanionic aggregates upon dialysis
Youlia Michina1, David Carriere, Clarisse Mariet
1CEA, IRAMIS, SCM, LIONS (Laboratoire Interdisciplinaire sur l'Organisation Nanométrique et Supramoléculaire), F-91191 Gif-sur-Yvette, France
Langmuir : the ACS Journal of Surfaces and Colloids
|January 30, 2009
Summary
Dialysis of catanionic surfactant mixtures reveals a critical 2:1 anionic/cationic ratio. This ratio dictates aggregate morphology and the removal of ions and cationic surfactants, forming stable vesicles above this threshold.
Area of Science:
- Colloid and Surface Science
- Materials Science
Background:
- Catanionic surfactant mixtures exhibit complex phase behavior and self-assembly.
- Understanding dialysis behavior is crucial for controlling surfactant removal and aggregate stability.
Purpose of the Study:
- To investigate the dialysis behavior of catanionic surfactant mixtures.
- To determine the influence of surfactant ratio on aggregate morphology and stability.
- To explore the potential of catanionic vesicles for encapsulation.
Main Methods:
- High-Performance Liquid Chromatography (HPLC)
- Neutron Activation Analysis
- Confocal Microscopy
- Nuclear Magnetic Resonance (NMR) spectroscopy
Main Results:
- A specific anionic/cationic ratio (approximately 2:1) governs dialysis outcomes.
- Below the 2:1 ratio, ion pairs and cationic surfactants are readily eliminated, forming ill-defined aggregates.
- Above the 2:1 ratio, stable, micrometer-sized vesicles are formed, resistant to extensive dialysis and retaining 30% of ions.
- Increased surfactant interaction energy (1-2 kBT) within the bilayer halts dialysis.
Conclusions:
- The anionic/cationic ratio is a critical parameter controlling the dialysis of catanionic mixtures.
- Vesicles formed above the 2:1 ratio exhibit exceptional stability due to "frozen" bilayers.
- These stable vesicles show significant potential for durable encapsulation applications.
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