Perforated Vesicles as Intermediate Structures in the Transition from Vesicles to Micelles in Dilute Aqueous Systems Containing Long Chain Alcohols and Ionic Surfactants

Abstract

Morphologies of aggregates in mixtures of long chain alcohols (n-decanol, n-dodecanol, and oleyl alcohol) and cationic surfactants (cetylpyridinium chloride, cetyltrimethylammonium bromide, and chloride) in dilute aqueous salt solutions were investigated by cryogenic transmission electron microscopy. In all cases elongated micellar structures transformed into vesicles with increasing alcohol concentration. Perforated bilayer structures were clearly identified in systems with oleyl alcohol and CTAB, in particular in 0.100 M NaBr. Increasing the salt concentration to 0.200 M other aggregates dominated composed of threadlike, probably branched, and interconnected micelles. A gradual evolution of morphologies was observed with increasing alcohol content at the lower salt concentration: thread-like micelles (developing branching to some extent), perforated vesicles, coexisting perforated and smooth bilayer structures, only smooth bilayers, and finally also inverted strucutures.

Keywords:

• Cryogenic transmission electron microscopy
• perforated bilayer
• perforated vesicle
• thread-like micelles
• vesicle

This work was supported by The Swedish Research Council, Knut and Alice Wallenberg Foundation, and Carl Tryggers Foundation.

Notes

Part of the special issue, Surface and Colloid Chemistry Without Borders: An International Festschrift for Professor Per Stenius on the Occasion of His 70th Birthday.