Centro de Química Estrutural, Instituto Superior Técnico, Universidade de Lisboa, 1049-001 Lisboa, Portugal.
Phys Chem Chem Phys. 2019 Feb 13;21(7):3742-3751. doi: 10.1039/c8cp06509h.
In this work we demonstrate that mixtures of (hexane + perfluorohexane) above the upper critical solution temperature segregate by forming domains at the nanometric scale. 129Xe NMR spectra obtained for solutions of xenon in liquid mixtures of (hexane + perfluorohexane) as a function of temperature suggest the existence of domains richer in the hydrogenated component, in which xenon "prefers" to be solvated. The average local concentration within the xenon coordination sphere is at least 0.05 higher in hexane mole fraction than the nominal concentration of the mixture. Atomistic molecular dynamics simulations support this analysis in excellent agreement with the experimental data. Additionally, 129Xe NMR spectra in pure perfluoroalkanes allow a detailed analysis of the liquid structure, continuing that previously reported for the liquid alkanes. It should be emphasised that nano-segregation is here observed in fluids governed exclusively by dispersion interactions, in contrast to other examples in which hydrogen bonding and polarity play important roles. Given its simplicity, this case study is thus prone to have a general impact in understanding the early mechanisms of segregation, phase separation and self-assembly.
在这项工作中，我们证明了（正己烷+全氟己烷）混合物在上临界溶液温度以上通过在纳米尺度上形成域而分离。 氙在（正己烷+全氟己烷）液体混合物溶液中的 129Xe NMR 光谱随温度的变化表明存在富含氢化组分的域，其中氙“更喜欢”被溶剂化。 氙配位球内的平均局部浓度至少比混合物的名义浓度高 0.05。 原子分子动力学模拟非常好地支持了与实验数据的这种分析。 此外，纯全氟烷烃中的 129Xe NMR 光谱允许对液体结构进行详细分析，这延续了以前对液体烷烃的报道。 应该强调的是，纳米分离在这里观察到的是仅由色散相互作用控制的流体，与其他氢键和极性起重要作用的例子形成对比。 鉴于其简单性，因此这种案例研究很可能对理解分离、相分离和自组装的早期机制产生普遍影响。
