Essafri I, Ghoufi A
Institut de Physique de Rennes, UMR 6251 CNRS, Université de Rennes, 263 avenue Général Leclerc, 35042 Rennes, France.
Phys Rev E. 2019 Jun;99(6-1):062607. doi: 10.1103/PhysRevE.99.062607.
The nonideality of binary mixtures is often related to the nature of the interactions between both liquids and of the heterogeneity at the nanoscale-named microstructure. When one of the liquids is a hydrogen bonds former and the second is aprotic, the progressive diluting of the hydrogen-bonding network leads to a clustering and nanophases. By considering two mixtures, toluene-methanol and cyclohexane-methanol, the nonideality and its connection with the structure at the nanoscale and the intermolecular interactions are numerically investigated. Contrary to the toluene that is fully miscible in methanol, cyclohexane presents a high range of immiscibility which makes it a relevant system to study the nucleation (local segregation) and its propagation. In both mixtures, the deviation from the ideal behavior is observed. In the case of the toluene-methanol mixture, the initial hydrogen-bonding network corresponding to a homogenous structure is locally broken due to the favorable toluene-methanol interactions leading to the spatial heterogeneity at the origin of the nonideality. In the range of miscibility of the cyclohexane-methanol mixtures, the formation of hydrophobic nanophases of larger size is observed due to the unfavorable interactions between both components leading to a self-organizing of cyclohexane molecules. The immiscibility of cyclohexane and methanol are then correlated to the formation of nanophases and their propagation, which are also at the origin of the spatial heterogeneity. In the pure methanol, we highlight the disconnection between the clustering and the heterogeneity. We shed light on the fact that the prepeak observed in the structure factor is independent of the degree of heterogeneity, but is connected to the presence of cyclic clusters.
二元混合物的非理想性通常与两种液体之间相互作用的性质以及纳米尺度上的不均匀性（即微观结构）有关。当其中一种液体是氢键形成体而另一种是质子惰性溶剂时，氢键网络的逐渐稀释会导致聚集和纳米相的形成。通过考虑两种混合物，甲苯 - 甲醇和环己烷 - 甲醇，对非理想性及其与纳米尺度结构和分子间相互作用的联系进行了数值研究。与能与甲醇完全互溶的甲苯不同，环己烷呈现出较大的不互溶范围，这使其成为研究成核（局域偏析）及其传播的相关体系。在这两种混合物中，均观察到了与理想行为的偏差。在甲苯 - 甲醇混合物中，对应于均匀结构的初始氢键网络由于甲苯 - 甲醇之间有利的相互作用而局部被破坏，导致了非理想性起源处的空间不均匀性。在环己烷 - 甲醇混合物的互溶范围内，由于两种组分之间不利的相互作用导致环己烷分子的自组装，观察到了更大尺寸的疏水纳米相的形成。环己烷和甲醇的不互溶性随后与纳米相的形成及其传播相关联，而这也是空间不均匀性的起源。在纯甲醇中，我们强调了聚集与不均匀性之间的脱节。我们揭示了结构因子中观察到的前峰与不均匀程度无关，但与环状簇的存在有关这一事实。
