Vesicles formed by sonication of aqueous dispersions of liquid crystals of the double-tailed surfactant sodium 4-(1′-heptylnonyl)benzenesulfonate (SHBS) are examined with several techniques. The average diameter of the vesicles prepared in water is about 450 Å. The average size decreases when prepared in NaCl or at higher surfactant concentrations. The presence of a few large liquid crystallites in the dispersion, as detected by fast-freeze cold-stage transmission electron microscopy, is shown to severely bias the measurement of vesicle sizes by quasi-elastic light-scattering techniques. The commonly used techniques of gel-permeation chromatography and ultrafiltration are shown to be ineffective in separating liquid crystals from SHBS vesicle dispersions. Vesicle preparation in the presence of uranyl acetate is shown to dramatically reduce the vesicle size. The spontaneous, irreversible reversion of vesicles to liquid crystallites as the dispersions age is documented and proves that SHBS vesicles are not equilibrium structures in water or brine.
|Original language||English (US)|
|Number of pages||20|
|Journal||Journal of Colloid And Interface Science|
|State||Published - Dec 1982|
Bibliographical noteFunding Information:
This work was supported by the Department of Energy, We are deeply grateful to Dr. V. A. Bloomfield for the use of his quasi-elastic light-scattering facility and