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Core Freezing and Size Segregation in Surfactant Core-Shell Micelles
Beatrice Plazzotta1, Jing Dai2, Manja A Behrens1
1†Interdisciplinary Nanoscience Center (iNANO) and Department of Chemistry, Aarhus University, Gustav Wieds Vej 14, 8000 Aarhus C, Denmark.
The Journal of Physical Chemistry. B
|July 31, 2015
Summary
Binary mixtures of poly(ethylene oxide) surfactants exhibit a core freezing-melting phase transition. This transition causes a reversible segregation of surfactants from mixed micelles into distinct micellar types.
Area of Science:
- Physical Chemistry
- Materials Science
- Colloid Science
Background:
- Nonionic poly(ethylene oxide) surfactants form biocompatible core-shell micelles.
- Previous studies identified a freezing-melting phase transition in the micellar core of single-component surfactants (CnEm).
Purpose of the Study:
- To investigate the low-temperature behavior of binary surfactant systems.
- To determine if core freezing/melting occurs in mixed surfactant micelles.
- To understand the impact of the phase transition on micelle composition.
Main Methods:
- Small-angle X-ray scattering (SAXS)
- Differential scanning calorimetry (DSC)
- Nuclear magnetic resonance (NMR)
- Density measurements
Main Results:
- Core freezing/melting was confirmed in binary mixtures of C18E20 and C18E100 surfactants.
- SAXS data revealed that the phase transition induces reversible segregation of surfactants.
- Surfactants transition from mixed micelles to distinct micelles of each component.
Conclusions:
- The core freezing-melting transition is a key phenomenon in both single and binary nonionic surfactant systems.
- This transition drives the self-assembly of surfactants into segregated micellar structures.
- Understanding this behavior is crucial for applications involving surfactant mixtures.
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