Department of Chemical and Environmental Engineering, Yale University, New Haven, Connecticut, USA.
J Phys Chem B. 2011 Feb 17;115(6):1403-10. doi: 10.1021/jp109882r. Epub 2011 Jan 27.
Micellization of the ionic surfactant sodium hexyl sulfate has been studied using atomistic explicit-solvent molecular dynamics simulations with and without excess NaCl or CaCl(2). Simulations were performed at surfactant loadings near the critical micellization concentration. Equilibrium micelle size distributions and estimates of the critical micellization concentration obtained from the simulations are in agreement with experimental data. In comparison to the sodium dodecyl sulfate surfactant, the shorter alkyl chain of sodium hexyl sulfate results in increased disorder of the micellar core and water exposure of the hydrocarbon tail groups. However, water and ions do not penetrate into the micellar core even for these weakly micellizing surfactants. Excess NaCl is observed to have a minor influence on the micelle structure but excess CaCl(2) induces drastic changes both in the structure and the dynamics of the micellar system. Furthermore, in the absence of excess salt, sodium hexyl sulfate forms predominantly spherical, disorganized aggregates but an increase in ionic strength drives an increase in aggregate size and leads to prolate aggregates.
使用带有和不带有过量 NaCl 或 CaCl(2)的原子显式溶剂分子动力学模拟研究了离子表面活性剂十六烷基硫酸钠的胶束化。模拟在接近临界胶束浓度的表面活性剂负载下进行。模拟得到的平衡胶束大小分布和临界胶束浓度的估计值与实验数据一致。与十二烷基硫酸钠表面活性剂相比，十六烷基硫酸钠较短的烷基链导致胶束核的无序度增加，并且烃尾基团暴露于水中。然而，即使对于这些弱胶束化的表面活性剂，水和离子也不会渗透到胶束核中。观察到过量的 NaCl 对胶束结构的影响较小，但过量的 CaCl(2)会导致胶束系统的结构和动力学发生剧烈变化。此外，在没有过量盐的情况下，十六烷基硫酸钠主要形成无规的球形聚集体，但离子强度的增加会导致聚集体尺寸增加，并导致长形聚集体的形成。
