Departamento de Fı́sica y Matemáticas , Universidad Iberoamericana, Prolongación Paseo de la Reforma , 880 , Lomas de Santa Fe, C.P. 01219 Ciudad de México , México.
Laboratorio de Simulación, Unidad Cuernavaca, Instituto de Matemáticas , Universidad Nacional Autónoma de México , A.P. 273-3 Admon. 3 , Cuernavaca , Morelos 62251 , México.
Langmuir. 2018 Mar 6;34(9):3146-3157. doi: 10.1021/acs.langmuir.7b03719. Epub 2018 Feb 19.
The process of equilibration of the tetradecane-water interface in the presence of sodium hexadecane-benzene sulfonate is studied using intensive atomistic molecular dynamics simulations. Starting as an initial point with all of the surfactants at the interface, it is obtained that the equilibration time of the interface (several microseconds) is orders of magnitude higher than previously reported simulated times. There is strong evidence that this slow equilibration process is due to the aggregation of surfactants molecules on the interface. To determine this fact, temporal evolution of interfacial tension and interfacial formation energy are studied and their temporal variations are correlated with cluster formation. To study cluster evolution, the mean cluster size and the probability that a molecule of surfactant chosen at random is free are obtained as a function of time. Cluster size distribution is estimated, and it is observed that some of the molecules remain free, whereas the rest agglomerate. Additionally, the temporal evolution of the interfacial thickness and the structure of the surfactant molecules on the interface are studied. It is observed how this structure depends on whether the molecules agglomerate or not.
使用强化原子分子动力学模拟研究了十四烷-水界面存在的十六烷基苯磺酸钠的平衡过程。从所有表面活性剂都在界面的初始点开始，可以得到界面的平衡时间（数微秒）比以前报道的模拟时间高出几个数量级。有强有力的证据表明，这种缓慢的平衡过程是由于表面活性剂分子在界面上的聚集。为了确定这一事实，研究了界面张力和界面形成能的时间演化，并将它们的时间变化与簇形成相关联。为了研究簇的演化，作为时间的函数，获得了平均簇大小和随机选择的表面活性剂分子自由的概率。估计了簇大小分布，观察到一些分子仍然是自由的，而其余的则聚集在一起。此外，还研究了界面厚度和界面上表面活性剂分子结构的时间演化。观察到这种结构取决于分子是否聚集。
