Thermodynamically Stable Vesicle Formation and Vesicle-to-Micelle Transition of Single-Tailed Anionic Surfactant in Water

Abstract

The aggregation behavior of sodium 3,6,9,12,15-pentaoxa-heptacosanoate (AEC4-Na) in aqueous solution with increase of the concentration at 25 °C was investigated using differential scanning calorimetry, equilibrium surface tension, solubilization of an oil-soluble dye, steady-state fluorescence, dynamic light scattering, and freeze-fractured transmission electron microscopy. Vesicle formation of AEC4-Na preceded micelle formation below the critical micelle concentration (cmc). The vesicle-to-micelle transition was observed through a narrow concentration region above the cmc. The mean diameters of the vesicles and micelles were not affected by the concentration. All solutions over a wide range of concentrations were homogeneously transparent with a low Krafft point below 0 °C. These results indicate that the AEC4-Na vesicles have a thermodynamically stable structure. Vesicle formation may be caused by a pseudobinary mixed surfactant system composed of monomeric AEC4-Na and an acid soap that consists of a dimer complex formed between AEC4-Na and unneutralized AEC4-Na. The thermodynamic stability would then result from the inhibition of close intermolecular aggregation and flexibility of the molecular shape in the vesicles due to the oxyethylene units in AEC4-Na.

One-step procedure for the preparation of functional polysaccharide/fatty acid multilayered coatings

“…Self-assembly in aqueous solutions. AECs with a lauric (C 12 ) or oleic (C 18:1 ) aliphatic chain and an average of 5 EO units form vesicles in a narrow pH range of 4-4.5, close to the pKa value of the fatty acid [27][28][29] the oppositely charged biopolymer chitosan ( Fig. 1b), welldefined onion-like vesicles are formed 24 , represented schematically in Fig.…”

Advantage of Sodium Polyoxyethylene Lauryl Ether Carboxylate as a Mild Cleansing Agent

“…Recently, Sakai et al reported a unique self-assembled structure formation of EC in a solution; EC forms vesicles at a concentration below the CMC and vesicle-to-micelle transition occurs above the CMC [39]. This unique aggregation behavior of EC is caused by a pseudo-binary mixed surfactant system composed of a monomeric EC and an acid soap that consist of a dimer complex in the solution.…”

Self-assembling systems based on quaternized derivatives of 1,4-diazabicyclo[2.2.2]octane in nutrient broth as antimicrobial agents and carriers for hydrophobic drugs

“…The vesicle-to-micelle transitions have been described previously [60,61]; however, to describe the type of structures formed in CMC range requires additional experimental verification. One of the methods successfully used to determine the morphology of aggregates makes use of DPH fluorescent probes [62][63][64].…”