Short haired wormlike micelles in mixed nonionic fluorocarbon surfactants
Suraj Chandra Sharma1, Carlos Rodríguez-Abreu, Lok Kumar Shrestha
1Graduate School of Environment and Information Sciences, Yokohama National University, Tokiwadai 79-7, Hodogaya-ku, Yokohama 240-8501, Japan.
Journal of Colloid and Interface Science
|June 26, 2007
Summary
This study reveals how mixing two fluorinated surfactants, C(8)F(17)EO(20) and C(8)F(17)EO(10), transforms spherical micelles into wormlike micelles. This transition alters solution viscosity and flow behavior, confirmed by rheology and SAXS.
Area of Science:
- Colloid and Surface Science
- Materials Science
- Rheology
Background:
- Nonionic fluorinated surfactants form micelles in aqueous solutions.
- The structure of these micelles dictates the solution's rheological properties.
- Understanding micellar transitions is key to designing functional fluids.
Purpose of the Study:
- To investigate the rheological behavior of mixed nonionic fluorinated surfactant systems.
- To determine the structural changes in micelles upon varying surfactant composition.
- To correlate micellar structure with observed viscoelastic properties.
Main Methods:
- Rheological measurements (viscosity, oscillatory shear) were performed on mixed surfactant solutions.
- Small-angle X-ray scattering (SAXS) was used to probe micellar structure.
- Systematic variation of surfactant concentrations and temperature was employed.
Main Results:
- C(8)F(17)EO(20) forms Newtonian solutions with spherical micelles.
- Addition of C(8)F(17)EO(10) induces shear-thinning behavior, indicating wormlike micelle formation.
- Viscosity unexpectedly increases with C(8)F(17)EO(20) addition, attributed to increased surfactant layer rigidity.
- SAXS confirms spherical micelles in C(8)F(17)EO(20) solutions and one-dimensional micellar growth with C(8)F(17)EO(10) addition.
Conclusions:
- Mixed systems of C(8)F(17)EO(n) surfactants can transition from Newtonian to viscoelastic fluids.
- The formation of wormlike micelles is controllable by adjusting the ratio of C(8)F(17)EO(10) and C(8)F(17)EO(20).
- Rheological observations are consistent with structural changes elucidated by SAXS.
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