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 (M. Facchin et al., RSC Adv. 2017, 7, 15337–15341) 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, multi-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 neutron 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 co-exist in solution. Our simulations also provide indications about how to escape this region, to produce thermodynamically stable micellar forms.

中文翻译：

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极性反转的表面活性剂能否在非极性溶剂中自组装？

我们使用全原子和粗粒混合颗粒场分子
动力学模拟研究了在水和环己烷中极性相反的表面活性剂的自组装过程。与传统的表面活性剂不同，在最近的实验中提出的正在研究的分子（M. Facchin等，RSC Adv。2017，7，15337–15341）是
由刚性且致密的疏水性金刚烷部分和长而松散的三甘醇尾形成。在水中，我们报告了稳定的倒胶团的形成，其中金刚烷头聚在一起形成疏水核，尾巴与水形成氢键。相反，多微秒模拟不能提供在环己烷中稳定形成胶束的证据。通过与实验扩散常数和小角中子散射强度进行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，溶液中聚集和游离的表面活性剂状态共存。我们的模拟还提供了有关如何逃逸该区域以产生热力学稳定的胶束形式的指示。