Frasch Duncan M, Spiegel Daniel R
Department of Physics and Astronomy, Trinity University, San Antonio, Texas 78212, USA.
J Chem Phys. 2014 Sep 28;141(12):124507. doi: 10.1063/1.4896303.
Forced Rayleigh scattering is used to study the tracer diffusion of an azobenzene in binary combinations of polar solvents, including water. In the absence of water, the tracer diffusion coefficient D in the mixture lies between the diffusion coefficients within the pure solvents, on a curve that is reasonably close to the prediction of free-volume theory. If water is present, on the other hand, the diffusion coefficient displays a minimum that is less than the smaller of the two pure-solvent values. We attempt to understand the different behavior in water by concentrating on the fairly hydrophobic nature of the solute, leading to a first solvent shell that is hydrophobic on the inside and hydrophilic on the outside. We also believe that clusters of amphiphiles explain the observation that, in aqueous combinations, D is nearly constant above a certain amphiphile mole fraction.
强迫瑞利散射用于研究偶氮苯在包括水在内的极性溶剂二元组合中的示踪扩散。在无水情况下，混合物中的示踪扩散系数D介于纯溶剂中的扩散系数之间，其曲线与自由体积理论的预测相当接近。另一方面，如果存在水，扩散系数会出现一个最小值，该最小值小于两种纯溶剂值中的较小值。我们试图通过关注溶质相当疏水的性质来理解在水中的不同行为，这导致第一个溶剂壳内部疏水而外部亲水。我们还认为两亲物簇解释了以下观察结果：在水性组合中，高于一定的两亲物摩尔分数时，D几乎是恒定的。
