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Composition-insensitive highly viscous wormlike micellar solutions formed in anionic and cationic surfactant systems
Kenji Aramaki1, Suzuka Iemoto, Naoaki Ikeda
1Graduate School of Environment and Information Sciences, Yokohama National University, Yokohama, Japan. aramakik@ynu.ac.jp
Journal of Oleo Science
|March 20, 2010
Summary
This study explores the phase behavior and rheology of aqueous micellar solutions formed by cocoyl glutamate (CGT-n) and hexadecyl trimethylammonium salt (CTAB/CTAC). We observed complex viscosity changes and viscoelastic properties indicative of worm-like micelles.
Area of Science:
- Colloid and Surface Science
- Rheology
- Materials Science
Background:
- Aqueous micellar solutions are crucial in various industrial applications.
- Understanding the phase behavior and rheological properties of mixed surfactant systems is essential for optimizing their performance.
- Worm-like micelles exhibit unique viscoelastic properties relevant to advanced materials and formulations.
Purpose of the Study:
- To investigate the phase behavior and rheological properties of water/cocoyl glutamate neutralized with triethanol amine (CGT-n)/hexadecyl trimethylammonium salt (CTAB or CTAC) systems.
- To characterize the formation and behavior of worm-like micelles in these mixed surfactant systems.
- To analyze the influence of surfactant mixing fraction and degree of neutralization on solution viscosity and viscoelasticity.
Main Methods:
- Ternary phase diagrams were constructed at 25°C to map the micellar phase region.
- Rheological measurements, including zero-shear viscosity and frequency sweeps, were performed on selected samples.
- Viscoelastic properties were analyzed using storage (G") and loss (G") moduli and fitted to the Maxwell model.
Main Results:
- Aqueous micellar phases were observed across a wide composition range in the ternary phase diagrams.
- Unusual viscosity behavior, including multiple maxima, was observed in water/CGT-n/CTAB systems, particularly at n=1.2.
- Highly viscous solutions and typical viscoelastic behavior of worm-like micelles were confirmed through frequency sweep measurements, with relaxation times mirroring viscosity changes.
Conclusions:
- The water/CGT-n/CTAB/CTAC systems form extensive micellar phases with tunable rheological properties.
- The observed complex viscosity profiles and viscoelastic behavior are characteristic of worm-like micelle formation.
- These findings provide insights into the self-assembly and flow properties of mixed cationic surfactant systems, relevant for formulation science.
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