Pucci Carlotta, Barbetta Aurelio, Sciscione Fabiola, Tardani Franco, La Mesa Camillo
Department of Chemistry, La Sapienza University , Cannizzaro Building, P. le A. Moro 5, I-00185 Rome, Italy.
J Phys Chem B. 2014 Jan 16;118(2):557-66. doi: 10.1021/jp4110745. Epub 2014 Jan 2.
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.
将烷基三甲基溴化铵水溶液或二烷基二甲基铵水溶液与烷基硫酸钠和二烷磺酸盐混合。根据总的表面活性剂浓度、电荷和/或摩尔比，通过混合非化学计量的带相反电荷的物质形成阳离子-阴离子囊泡。所得囊泡在热力学和动力学上都是稳定的。通过ζ电位和动态光散射对体系进行了表征。通常，阳离子-阴离子囊泡的尺寸在10²-10³nm范围内，并带有大量的表面电荷。在固定的表面活性剂浓度下，囊泡表面电荷密度随摩尔比变化，当摩尔比接近1时趋于零。相反，当阳离子/阴离子摩尔比接近1时，流体动力学半径发散。双层厚度和表面电荷密度由摩尔比和NaBr的添加控制，NaBr在囊泡稳定性中起作用。盐屏蔽表面电荷密度并调节囊泡大小和双层厚度。略高浓度的NaBr会诱导从囊泡向层状相的转变。通过介电弛豫实验分析了阳离子-阴离子分散体的电动性质。所测量的性质对囊泡尺寸分布敏感。事实上，弛豫频率与囊泡多分散性成比例地移动。为此目的提出的模型计算支持了实验结果。
