Vesicles of a New Salt‐Free Cat‐anionic Fluoro/Hydrocarbon Surfactant System

Abstract

Weakly basic tetradecyldimethylaminoxide (C14DMAO) molecules can be protonated to form a cationic surfactant, C14DMAOH+, by an acidic fluorocarbon surfactant, an 8-2-fluorotelomer unsaturated acid (C7F15CF==CHCOOH), to form a salt-free cationic and anionic (cat-anionic) fluoro/hydrocarbon surfactant system in aqueous solution. The high Krafft point of C7F15CF==CHCOOH was largely reduced as a result of being mixed with a C14DMAO micelle solution. A study of the phase behavior of the new salt-free cat-anionic fluoro/hydrocarbon surfactant system clearly indicates the existence of a birefringent Lalpha-phase region at (25.0+/-0.1) degrees C. The birefringent Lalpha phase consists of vesicles, which include uni- and multilamellar vesicles with one to dozens of shells, and oligovesicular vesicles, as demonstrated by freeze-fracture and cryo-transmission electron microscopy (FF- and cryo-TEM) images. The size distribution and structural transitions in the salt-free cat-anionic fluoro/hydrocarbon surfactant system were studied by dynamic light scattering (DLS) and 1H and 19F NMR spectroscopy. The formation of a salt-free cat-anionic vesicle phase could be induced by the strong electrostatic interaction between the cationic hydrocarbon C14DMAOH+ and the anionic fluorocarbon C7F15CF==CHCOO-, which provided evidence that the electrostatic interaction between the cationic and anionic surfactants is larger than the nonsynergistic interaction between the stiff fluorocarbon and the soft hydrocarbon chains of the surfactants.

Rheology of wormlike micelles in mixed solutions of cocoamidopropyl betaine and sodium dodecylbenzenesulfonate

“…4a and b show the polarization micrographs of the cloudy solutions containing 0.1 and 0.115 M of SDBS, respectively. These images prove that these solutions are birefringent and the observed cross-like textures demonstrate the existence of the bilayer phase [31,32].…”

Polymer–vesicle association

“…Another interesting case to analyse is that of salt-free catanionic surfactants, for which spontaneous vesiculation in zero salt concentration and without excess of ionic surfactant has also been reported to occur [46,[126][127][128][129][130][131][132][133][134][135]. These systems have the further advantage that the effect of electrostatic interactions can be studied in a controlled way by the addition of salt.…”

Self-assembly of metal–ligand coordinated charged vesicles

“…Novel self-assembled structures can form because of the absence of the excess salts without screened electrostatic repulsions by salts [25 • -27 • ]. More salt-free catanionic surfactant systems consisting of uni-and multilamellar vesicles were systematically studied [28][29][30][31][32]. Very recent, a system of an excellent extractant of rare earth metal ions, di(2-ethylhexyl) phosphate (HDEHP, commercial name P204), mixing with a cationic trimethyltetradecylammonium hydroxide (TTAOH) in water was studied [33].…”