Yoshida N, Matsuoka K, Moroi Y
Faculty of Science, Kyushu University, Higashi-ku, Fukuoka, 812-81, Japan
J Colloid Interface Sci. 1997 Mar 15;187(2):388-95. doi: 10.1006/jcis.1996.4691.
Critical micelle concentrations (CMCs) of three ionic surfactants that contain n-decyltrimethylammonium ion as a surfactant cation and bromide, perfluoroacetate, and perfluoropropionate anions as a counterion, respectively, were determined by electrical conductivity at several temperatures. The degrees of counterion binding to micelle were obtained at the same temperatures as the change in CMC with total counterion concentration. Molecular weights of micelles were determined by static light scattering. The change in monomeric surfactant ion concentration with total surfactant concentration was determined by membrane potential measurement. The mass-action model was applied to micelle formation to calculate the three micellization parameters: micellization constant, micelle aggregation number, and number of counterions per micelle. Thermodynamic parameters (DeltaG0, DeltaH0, DeltaS0) of the micelle formations were calculated from the temperature dependence of these parameters. At lower temperatures micellization has been found to be entropy driven, whereas it is enthalpy driven at higher temperatures. For n-decyltrimethylammonium perfluoropropionate, however, the tendency is quite different from those of other surfactants. The micellization parameters also made it possible to evaluate the concentration change of monomeric surfactant ion with total surfactant concentration. The evaluated concentration explains the results from the membrane potential measurement.
分别以溴离子、全氟乙酸根离子和全氟丙酸根离子作为抗衡离子，以正癸基三甲基铵离子作为表面活性剂阳离子的三种离子型表面活性剂的临界胶束浓度（CMC），在几个温度下通过电导率测定。在与CMC随总抗衡离子浓度变化相同的温度下，获得抗衡离子与胶束的结合程度。通过静态光散射测定胶束的分子量。通过膜电位测量确定单体表面活性剂离子浓度随总表面活性剂浓度的变化。将质量作用模型应用于胶束形成，以计算三个胶束化参数：胶束化常数、胶束聚集数和每个胶束的抗衡离子数。根据这些参数的温度依赖性计算胶束形成的热力学参数（ΔG0、ΔH0、ΔS0）。发现在较低温度下胶束化是由熵驱动的，而在较高温度下是由焓驱动的。然而，对于正癸基三甲基铵全氟丙酸盐，其趋势与其他表面活性剂的趋势有很大不同。胶束化参数还使得评估单体表面活性剂离子浓度随总表面活性剂浓度的变化成为可能。评估的浓度解释了膜电位测量的结果。
