Ion distribution around synthetic vesicles of the cat-anionic type
| Autor: | Franco Tardani, Camillo La Mesa, Fabiola Sciscione, Carlotta Pucci, Aurelio Barbetta |
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| Jazyk: | angličtina |
| Rok vydání: | 2014 |
| Předmět: |
Bromides
Hydrodynamic radius Lipid Bilayers Analytical chemistry Surface-Active Agents Electrokinetic phenomena Dynamic light scattering Pulmonary surfactant dls synthetic vesicles zeta-potential ion distribution Cations Materials Chemistry Scattering Radiation Surface charge Physical and Theoretical Chemistry Aqueous solution Cetrimonium Chemistry Vesicle Charge density Sodium Compounds Surfaces Coatings and Films Cetrimonium Compounds |
| Popis: | Aqueous alkyltrimethylammonium bromides, or dialkyldimethylammonium ones, were mixed with sodium alkyl sulfates and dialkanesulfonates. Depending on the overall surfactant concentration, charge and/or mole ratios, cat-anionic vesicles were formed by mixing nonstoichiometric amounts of oppositely charged species. The resulting vesicles are thermodynamically and kinetically stable. ζ-potential and dynamic light scattering characterized the systems. As a rule, cat-anionic vesicles have sizes in the 10(2)-10(3) nm range and bear significant amounts of surface charges. At fixed surfactant concentration, the vesicle surface charge density scales with mole ratios and tends to zero as the latter approach unity. Conversely, the hydrodynamic radius diverges when the cationic/anionic mole ratio is close to 1. The double-layer thickness and surface charge density are controlled by mole ratios and addition of NaBr, which plays a role in vesicle stability. The salt screens the surface charge density and modulates both vesicle size and double-layer thickness. Slightly higher concentrations of NaBr induce the transition from vesicles toward lamellar phases. The electrokinetic properties of cat-anionic dispersions were analyzed by dielectric relaxation experiments. The measured properties are sensitive to vesicle size distributions. In fact, the relaxation frequency shifts in proportion to vesicle polydispersity. Model calculations proposed on that purpose supported the experimental findings. |
| Databáze: | OpenAIRE |
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