Institut de Chimie Séparative de Marcoule (ICSM), UMR 5257, CEA-CNRS-Université Montpellier-ENSCM, Site de Marcoule, Bâtiment 426, BP 17171, F-30207 Bagnols-sur-Cèze Cedex, France.
Soft Matter. 2017 Aug 23;13(33):5518-5526. doi: 10.1039/c7sm00733g.
The bending rigidity of small reverse aggregates involved in liquid-liquid extraction processes has been investigated by molecular dynamics simulations. Simulations of a common extractant (DMDOHEMA) with four hydrophobic chains in explicit solvent (n-heptane) and in vacuum have been performed to determine the effect of solvent penetration on film stiffness. Elastic film bending energy that is needed for mesoscopic modelling of transfer of species between complex fluids is harmonic in terms of curvature (Helfrich formalism) and the packing parameter only if the solvent is explicitly taken into account. In terms of the packing parameter of the real molecular film constituting the reverse water in oil aggregates and taking into account molecular volume, area and film thickness (that is in agreement with Tanford's model), the bending rigidity is calculated to be about 16 kT per extractant molecule (about 40 kJ mol), which is smaller than the free energy of transfer from an isolated "monomer" molecule to a weak aggregate, but of the order of magnitude of the free energy of transfer used in liquid-liquid extraction processes.
通过分子动力学模拟研究了涉及液-液萃取过程的小反向聚集体的弯曲刚度。在显式溶剂（正庚烷）和真空中对具有四个疏水链的常见萃取剂（DMDOHEMA）进行了模拟，以确定溶剂渗透对膜刚度的影响。对于在复杂流体之间转移物种的介观建模，弹性膜弯曲能是曲率的调和函数（Helfrich 形式），仅当考虑溶剂时才与 packing 参数相关。根据构成反向水包油聚集体的实际分子膜的 packing 参数，并考虑分子体积、面积和膜厚度（与 Tanford 模型一致），计算得到每个萃取剂分子的弯曲刚度约为 16 kT（约 40 kJ/mol），这小于从孤立“单体”分子到弱聚集体的转移自由能，但与液-液萃取过程中使用的转移自由能数量级相当。
