Department of Physical Chemistry, Tarbiat Modares University , P.O. Box 14115-117, Tehran, Iran.
J Phys Chem B. 2014 Mar 20;118(11):3063-73. doi: 10.1021/jp4123908. Epub 2014 Mar 6.
Self-assembly of pure ester-containing cationic gemini surfactants, dodecyl esterquat, and dodecyl betainate geminis, and cation-rich catanionic mixtures of them with sodium dodecyl sulfate (SDS) were investigated using surface tension, electrical conductivity, dynamic light scattering (DLS), transmission electron microscopy (TEM) and cyclic voltammetry (CV) measurements in the absence and presence of KCl. Different physicochemical properties such as the critical micelle concentration (CMC), degree of counterion dissociation (αdiss), interfacial properties, morphology of aggregates, and interparticle interaction parameters were determined. Both geminis formed micelles in the absence of KCl, and mixing with SDS did not change the morphology; just a growth in micelle size was observed. However, the aggregation behavior of these geminis with respect to the position of the ester bond in the alkyl chain appeared completely different in the presence of KCl. Esterquat gemini formed cubic nanoparticles (or cobosomes) in the presence of [KCl] = 0.05 M and transformed into spherical micelles upon increasing the surfactant concentration. By contrast, betainate gemini formed vesicles in the presence of [KCl] = 0.05 M and subsequently converted to micelles as the surfactant concentration increased. The morphology of esterquat gemini (in the presence of 0.05 M KCl) after mixing with SDS changed from cubic nanoparticles (or cobosomes) to cylindrical nanoparticles coexistent with cobosomes. Betainate gemini remained vesicular upon mixing with SDS, and no dramatic structural change of aggregates took place. The morphology changes of aggregates upon mixing with SDS were explained from calculating the interactions between two gemini surfactants and SDS on the basis of regular solution theory.
纯酯基阳离子双子表面活性剂十二酯季铵盐和十二烷基甜菜碱双子表面活性剂的自组装，以及它们与十二烷基硫酸钠（SDS）的阳离子富的反离子混合物的自组装，使用表面张力、电导率、动态光散射（DLS）、透射电子显微镜（TEM）和循环伏安法（CV）在不存在和存在 KCl 的情况下进行了研究。测定了不同的物理化学性质，如临界胶束浓度（CMC）、抗衡离子离解度（αdiss）、界面性质、聚集形态和颗粒间相互作用参数。两种双子表面活性剂在不存在 KCl 的情况下形成胶束，与 SDS 混合不会改变形态；只观察到胶束尺寸的增长。然而，这些双子表面活性剂在烷基链酯键位置上的聚集行为在存在 KCl 时完全不同。酯基季铵盐双子表面活性剂在[KCl]=0.05 M 存在下形成立方纳米颗粒（或胶束），并随着表面活性剂浓度的增加转化为球形胶束。相比之下，甜菜碱双子表面活性剂在[KCl]=0.05 M 存在下形成囊泡，并随着表面活性剂浓度的增加转化为胶束。在 0.05 M KCl 存在下混合 SDS 后，酯基季铵盐双子表面活性剂的形态从立方纳米颗粒（或胶束）转变为与胶束共存的圆柱形纳米颗粒。在混合 SDS 后，甜菜碱双子表面活性剂仍保持囊泡状态，聚集形态没有发生明显变化。根据正规模论，从计算两种双子表面活性剂与 SDS 之间的相互作用的角度解释了混合 SDS 后聚集形态的变化。
