Osmotic pressure and interparticle interactions in ionic micellar surfactant solutions
Osmotic pressure and interparticle interactions in ionic micellar surfactant solutions
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DOI：
10.1021/jp9805407
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发表时间：
1998-04-09
影响因子：
3.3
通讯作者：
Radke, CJ
中科院分区：
文献类型：
--
作者：
Amos, DA;Markels, JH;Radke, CJ
给出了胶束表面活性剂浓溶液的渗透压计算结果。使用无压膜渗透计，我们测量了阳离子表面活性剂十六烷基氯化吡啶（CPC）和阴离子表面活性剂十二烷基硫酸钠（SDS）溶液在0.01 M氯化钠中的渗透压。纳滤膜作为半透性屏障，允许测量跨越胶束区域的体积分数的大渗透压，范围从略高于临界胶束浓度（cmc）到0.18的体积分数。SDS和CPC的大渗透压分别高达323和250 kPa，被解释为强胶束相互作用的证据。为了量化这些大渗透压，我们开发了一个自一致的活度系数模型，其中明确包括表面活性剂单体、胶束聚集体和电解质分子。使用boublikk - mansoori状态方程考虑了排除体积效应，使用平均球面近似（MSA）对胶束间静电相互作用进行了建模。我们将活度系数模型与先前开发的理想质量-作用模型结合起来，用于cmc附近无限稀聚集体浓度下的胶束平衡常数。(1)所得的非理想热力学模型用于描述胶束聚集体和表面活性剂单体在高浓度下的平衡。在模型的热力学框架内考虑了导致背景电解质重新分布的Donnan膜效应。将该自洽模型与新的渗透压实验数据进行了比较。
Results are presented for the osmotic pressure of concentrated aqueous micellar surfactant solutions. Using a pressure-nulled membrane osmometer, we measure the osmotic pressure of solutions of the cationic surfactant, cetylpyridinium chloride (CPC), and the anionic surfactant, sodium dodecyl sulfate (SDS), in 0.01 M sodium chloride. Nanofiltration membranes serve as the semipermeable barrier and permit measurement of large osmotic pressures over volume fractions that span the micellar region ranging from just above the critical micelle concentration (cmc) up to volume fractions of 0.18. Large osmotic pressures, up to 323 and 250 kPa for SDS and CPC, respectively, are interpreted as evidence of strong intermicellar interactions. To quantify these large osmotic pressures, we develop a self-consistent activity-coefficient model that includes explicitly the surfactant monomer, micellar aggregates, and electrolyte molecules. Excluded-volume effects are taken into account using the Boublik-Mansoori equation of state, and intermicellar electrostatic interactions are modeled using the mean spherical approximation (MSA). We combine the activity-coefficient model with an ideal mass-action model developed previously for the micelle equilibrium constants at infinitely dilute aggregate concentrations in the vicinity of the cmc.(1) The resulting nonideal thermodynamic model is used to describe the equilibrium between the micellar aggregates and the surfactant monomer at elevated concentrations. The Donnan membrane effect, which leads to the redistribution of background electrolyte, is accounted for within the thermodynamic framework of the model. Successful comparison is made between the proposed self-consistent model and the new experimental osmotic pressure data.