Department of Chemistry and Hylleraas Centre for Quantum Molecular Sciences, University of Oslo, P.O. Box 1033, Blindern, 0315 Oslo, Norway.
Department of Physics and Institute for Fundamental Science, University of Oregon, Eugene, Oregon 97403, United States.
J Phys Chem B. 2020 Jul 23;124(29):6448-6458. doi: 10.1021/acs.jpcb.0c04842. Epub 2020 Jul 14.
We investigate the self-assembly process of a surfactant with inverted polarity in water and cyclohexane using both all-atom and coarse-grained hybrid particle-field molecular dynamics simulations. Unlike conventional surfactants, the molecule under study, proposed in a recent experiment, is formed by a rigid and compact hydrophobic adamantane moiety, and a long and floppy triethylene glycol tail. In water, we report the formation of stable inverted micelles with the adamantane heads grouping together into a hydrophobic core and the tails forming hydrogen bonds with water. By contrast, microsecond simulations do not provide evidence of stable micelle formation in cyclohexane. Validating the computational results by comparison with experimental diffusion constant and small-angle X-ray scattering intensity, we show that at laboratory thermodynamic conditions the mixture resides in the supercritical region of the phase diagram, where aggregated and free surfactant states coexist in solution. Our simulations also provide indications as to how to escape this region to produce thermodynamically stable micellar aggregates.
我们使用全原子和粗粒混合粒子场分子动力学模拟研究了一种在水和环己烷中具有反转极性的表面活性剂的自组装过程。与传统表面活性剂不同，研究中使用的分子是由刚性和紧凑的疏水金刚烷部分和长而柔软的三乙二醇尾部分组成的，最近的实验提出。在水中，我们报告了稳定的反相胶束的形成，其中金刚烷头聚集在一起形成疏水性核心，而尾部与水形成氢键。相比之下，微秒模拟并没有提供在环己烷中稳定胶束形成的证据。通过与实验扩散常数和小角度 X 射线散射强度的比较来验证计算结果，我们表明在实验室热力学条件下，混合物位于相图的超临界区域，其中聚集态和游离态表面活性剂共存于溶液中。我们的模拟还提供了如何摆脱这种区域以产生热力学稳定胶束聚集体的线索。
