Self-assembly of mixed anionic and nonionic surfactants in aqueous solution
1Institut Laue Langevin, DS/LSS, 6 rue Jules Horowitz, B.P. 156, 38042 Grenoble Cedex 9. grillo@ill.eu
Langmuir : the ACS Journal of Surfaces and Colloids
|May 21, 2011
Summary
This study reveals how mixing two surfactants, AOT and C(12)E(4), in heavy water (D(2)O) creates unique micellar structures and phase behaviors not seen in single-surfactant systems.
Area of Science:
- Colloid and Surface Science
- Materials Science
- Physical Chemistry
Background:
- Binary surfactant mixtures offer complex phase behavior.
- Understanding aggregate formation is key to designing new materials.
- AOT and C(12)E(4) are common surfactants with distinct properties.
Purpose of the Study:
- To map the phase diagram of AOT and C(12)E(4) in D(2)O.
- To characterize the microstructures formed by these binary mixtures.
- To investigate the influence of composition and concentration on aggregate formation.
Main Methods:
- Surface tension measurements.
- Small-angle neutron scattering (SANS).
- Phase diagram construction.
Main Results:
- The micellar region is significantly extended in composition and concentration.
- Spherical micelles form in AOT-rich regions.
- Cylindrical micelles (80-300 Å length) form in C(12)E(4)-rich regions.
- Swollen lamellar phases and mixed micellar/lamellar phases are observed at higher and intermediate concentrations, respectively.
Conclusions:
- Binary mixtures of AOT and C(12)E(4) in D(2)O exhibit extended and unique phase behavior.
- The type and size of aggregates are tunable by adjusting concentration and molar ratio.
- Electrostatic repulsions play a dominant role in the formation of swollen lamellar phases.
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