Comez L, Paolantoni M, Lupi L, Sassi P, Corezzi S, Morresi A, Fioretto D
†IOM-CNR c/o Dipartimento di Fisica e Geologia, Università di Perugia, Via Pascoli, I-06123 Perugia, Italy.
‡Dipartimento di Fisica e Geologia, Università di Perugia, Via Pascoli, I-06123 Perugia, Italy.
J Phys Chem B. 2015 Jul 23;119(29):9236-43. doi: 10.1021/jp509854a. Epub 2014 Dec 15.
Molecular dynamics and structural properties of water-tert-butyl alcohol (TBA) mixtures are studied as a function of concentration by extended depolarized light scattering (EDLS) experiments. The wide frequency range, going from fraction to several thousand GHz, explored by EDLS allows distinguishing TBA rotational dynamics from structural relaxation of water and intermolecular vibrational and librational modes of the solution. Contributions to the water relaxation originating from two distinct populations, i.e. hydration and bulk water, are clearly identified. The dynamic retardation factor of hydration water with respect to the bulk, ξ ≈ 4, almost concentration independent, is one of the smallest found by EDLS among a variety of systems of different nature and complexity. This result, together with the small number of water molecules perturbed by the presence of TBA, supports the idea that hydrophobic simple molecules are less effective than hydrophilic and more complex molecules in perturbing the H-bond network of liquid water. At increasing TBA concentrations the average number of perturbed water molecules shows a pronounced decrease and the characteristic frequency of librational motions reduces significantly, both of which are results consistent with the occurrence of self-aggregation of TBA molecules.
通过扩展去偏振光散射（EDLS）实验，研究了水 - 叔丁醇（TBA）混合物的分子动力学和结构性质随浓度的变化。EDLS所探索的从分数赫兹到数千吉赫兹的宽频率范围，使得能够区分TBA的旋转动力学与水的结构弛豫以及溶液的分子间振动和摆动模式。源自两个不同群体（即水合水和本体水）对水弛豫的贡献被清晰地识别出来。水合水相对于本体的动态延迟因子ξ≈4，几乎与浓度无关，是EDLS在各种不同性质和复杂性的系统中所发现的最小的值之一。这一结果，连同受TBA存在影响的水分子数量较少，支持了这样一种观点，即疏水性简单分子在扰乱液态水的氢键网络方面比亲水性和更复杂的分子效果更差。随着TBA浓度的增加，受扰动水分子的平均数显著下降，摆动运动的特征频率也显著降低，这两个结果都与TBA分子发生自聚集相一致。
