Water Aggregate in a Reversed Micelle and Hydrated Cluster in a Molecular Beam

已知位于生物聚合物附近的小水聚集体作为重要的反应介质。我们基于以下两种模型研究了这种水聚集体的性质：H_2O/异辛烷/ AOT（AerosolOT）反胶束溶液中的水池和超声分子束中形成的水化团簇。本文主要研究了一系列不同极性的芘基化合物芘磺酸钠（PSA^-Na^+）和8-乙酰氧基芘-1，3，6-三磺酸钠（APTSNa）在反胶束中的增溶作用。通过分析激光诱导的瞬态物种的时间曲线以及吸收光谱和荧光光谱，确定了探针分子在反胶束中的位置和分布。瞬态吸收光谱及其时间分布强烈依赖于水池的大小。这些依赖性可以用PSA^-或APTS在反胶束中的位置和分布来解释。综上所述，（1）PSA^-分子既存在于表面活性剂的水池中，也存在于表面活性剂的疏水部分。随着反胶束粒径的减小，PSA ^-在水相中的分布逐渐减少，大部分PSA^-分布在最小反胶束的疏水部分。另一方面，更极性的分子APTS主要分布在水池中。(2)足够大尺寸的水池以溶解水池中的这些芘基化合物。(3)这些分子在足够大的水池中的溶解度小于在本体水中的溶解度。只有少数水池含有两个以上的PSA^-或APTS分子。这些性质溶解的芘化合物在水池中形成的一个水合簇在超声束形成对比。这表明，围绕水池或束缚水的层强烈地影响溶质分子在水池中的增溶。

A small water aggregate located near a biopolymer is known to work as an important reaction medium. We have investigated the properties of such a water aggregate based on the following two model: Water pool in a reversed micellar solution from H_2O/isooctane/ AOT(Aerosol OT) and hydrated clusters formed in a supersonic molecular beam. In this work we mainly investigated solubilization of a series of pyrenyl compounds with different polarity, sodium pyrenesulfonate (PSA^-Na^+) and sodium 8-acetoxypyrene-1,3,6-trisulfonate (APTSNa), in the reversed micelle. The location and distribution of the probe molecules in the reversed micelle was determined by analyzing time profiles as well as absorption and fluorescence spectra of laser-induced transient species. The transient absorption spectra and their time profiles strongly depend on the size of water pool. Those dependences can be explained in terms of location and distribution of PSA^- or APTS in the reversed micelle. In conclusion, (1) PSA^- molecules are located both in the water pool and in the hydrophbic part of the surfactant. Its distribution in the water pool decreases with decrease of the size of water pool and most of PSA^- are located in the hydrophobic part in the smallest reversed micelle. On the other hand, more polar molecule, APTS, is predominantly distributed in the water pool. (2) A sufficiently large size of water pool to solubilize these pyrenyl compounds in the water pool. (3) Solubilities of these molecules in a sufficiently large water pool are less than those in bulk water. Only a small number of water pools contain more than two PSA^- or APTS moleculs. These properties for solubilization of pyrenyl compounds in the water pool are in contrast to a hydrated cluster formed in a supersonic beam. It suggests that the layer surrounding water pool or bound water strongly affects solubilization of a solute molecule in the water pool.