The University of Oklahoma School of Chemical, Biological, and Materials Engineering, Norman, Oklahoma 73019, USA.
Langmuir. 2010 Apr 20;26(8):5462-74. doi: 10.1021/la904615u.
The effect of surface coverage on the aggregate structure for the nonionic hexaethylene glycol monododecyl ether (C(12)E(6)) and anionic sodium dodecyl sulfate (SDS) surfactants at vacuum-water interface has been studied using molecular dynamics simulations. We report the aggregate morphologies and various structural details of both surfactants as a function of surface coverage. Our results indicate that C(12)E(6) tail groups orient less perpendicularly to the vacuum-water interface compared to SDS ones. Interfacial C(12)E(6) shows a transition from gaslike to liquidlike phases as the surface density increases. However, even at the largest coverage considered, interfacial C(12)E(6) aggregates show more disordered structures compared to SDS ones. Both surfactants exhibit a non-monotonic change in planar mobility as the available surface area per molecule varies. The results are interpreted on the basis of the molecular features of both surfactants, with particular emphasis on the properties of the surfactant heads, which are nonionic, long, and flexible for C(12)E(6), as opposed to ionic, compact, and rigid for SDS.
使用分子动力学模拟研究了在真空-水界面上非离子六乙二醇单十二醚（C（12）E（6））和阴离子十二烷基硫酸钠（SDS）表面活性剂的表面覆盖率对聚集结构的影响。我们报告了两种表面活性剂的聚集形态和各种结构细节作为表面覆盖率的函数。我们的结果表明，与 SDS 相比，C（12）E（6）的尾部基团与真空-水界面的取向不太垂直。随着表面密度的增加，界面 C（12）E（6）从气态向液态转变。然而，即使在考虑的最大覆盖度下，与 SDS 相比，界面 C（12）E（6）聚集物的结构更为无序。两种表面活性剂的平面迁移率都表现出非单调变化，这与每个分子的可用表面积有关。结果是基于两种表面活性剂的分子特征来解释的，特别强调了表面活性剂头的性质，对于 C（12）E（6）来说，表面活性剂头是非离子的、长的和灵活的，而对于 SDS 来说，表面活性剂头是离子的、紧凑的和刚性的。
