Sugihara G, Era Y, Funatsu M, Kunitake T, Lee S, Sasaki Y
Faculty of Science, Fukuoka University, Jonan-ku, Fukuoka, 814-80, Japan
J Colloid Interface Sci. 1997 Mar 15;187(2):435-42. doi: 10.1006/jcis.1996.4733.
Micelle formation was studied for four mixing combinations of dodecylammonium (DA) salts having perfluorocarboxylate ions (trifluoroacetate (PA) and pentafluoropropionate (PP) and alkane sulfonate ions (methane sulfonate (MS) and ethane sulfonate (ES)) as their counterions, i.e., DAPA/DAMS, DAPA/DAES, DAPP/DAMS, and DAPP/DAES. The fluorocarbon anions as counterions exhibited that the degree of counterion binding to micelle (beta) as well as the extent of stabilizing micelles and lowering ability of critical micellization concentration (CMC) are greater than hydrocarbon anions. The "mixed micelle formation" was examined in terms of CMC as a function of mole fraction (Xi) in each surfactant mixture. The CMCs of the mixed surfactant systems studied here, correspond to those of "surfactant with mixed counterions". However, by regarding tentatively those combinations as binary mixed surfactant systems, the CMC vs Xi curves (singly dispersed phase curves) as well as CMC vs micellar composition (Yi) curves (micellar phase curves) were simulated by applying the present authors' and Rubingh's equations which have been derived respectively with and without taking into account mutual added-salt effect (or the beta value for each pure system). A negative deviation from ideal mixing was observed for each combination, indicating that mixing of fluorocarbon anion with hydrocarbon anion as counterion of DA salts results in more stabilized micelle formation. Plotting the derivative of specific conductance (kappa) by total concentration of surfactant (Ct), dkappa/dCt against Ct, the curves showed a constant value at the sufficiently higher concentration range than CMC, and the constant values were found able to be related to the degree of dissociation of micelles (alpha). Even for the mixed systems, the alpha or beta values were estimated from the conductivity data. The greater power to stabilize micelle formation by fluorocarbon ions was interpreted on the basis of concept of "contact hydrophobic interaction" proposed by Mukerjee (Mukerjee, P., Colloids Surf. A: Physicochem. Eng. Aspects 84, 49 (1994)).
研究了以全氟羧酸根离子（三氟乙酸根（PA）和五氟丙酸根（PP））以及烷烃磺酸根离子（甲磺酸根（MS）和乙磺酸根（ES））作为反离子的十二烷基铵（DA）盐的四种混合组合的胶束形成情况，即DAPA/DAMS、DAPA/DAES、DAPP/DAMS和DAPP/DAES。作为反离子的碳氟阴离子表明，反离子与胶束的结合程度（β）以及稳定胶束的程度和降低临界胶束浓度（CMC）的能力都大于烃类阴离子。根据CMC作为每种表面活性剂混合物中摩尔分数（Xi）的函数来研究“混合胶束形成”。这里研究的混合表面活性剂体系的CMC与“具有混合反离子的表面活性剂”的CMC相对应。然而，通过暂时将这些组合视为二元混合表面活性剂体系，应用作者本人和鲁宾的方程分别模拟了CMC对Xi曲线（单分散相曲线）以及CMC对胶束组成（Yi）曲线（胶束相曲线），这些方程分别在考虑和不考虑相互加盐效应（或每个纯体系的β值）的情况下推导得出。每种组合都观察到与理想混合的负偏差，表明作为DA盐反离子的碳氟阴离子与烃类阴离子混合会导致形成更稳定的胶束。将比电导率（κ）对表面活性剂总浓度（Ct）的导数dkappa/dCt与Ct作图，在比CMC足够高的浓度范围内，曲线显示出一个恒定值，并且发现该恒定值与胶束的解离程度（α）有关。即使对于混合体系，也可以从电导率数据估算出α或β值。基于Mukerjee提出的“接触疏水相互作用”概念（Mukerjee, P., Colloids Surf. A: Physicochem. Eng. Aspects 84, 49 (1994)）解释了碳氟离子稳定胶束形成的更强能力。
