Geometry and Nanolength Scales versus Interface Interactions: Water Dynamics in AOT Lamellar Structures and Reverse Micelles
Geometry and Nanolength Scales versus Interface Interactions: Water Dynamics in AOT Lamellar Structures and Reverse Micelles
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DOI：
10.1021/ja901950b
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发表时间：
2009-06-17
影响因子：
15
通讯作者：
Fayer, M. D.
中科院分区：
文献类型：
--
作者：
Moilanen, David E.;Fenn, Emily E.;Fayer, M. D.
为了确定相对重要性的限制几何形状和纳米尺度与水/界面相互作用，水和界面之间的动态相互作用的研究与超快红外光谱。气溶胶OT（AOT）是一种表面活性剂，其可以形成具有已知水层厚度的二维层状结构以及具有已知水纳米池直径的明确定义的单分散球形反胶束。层状结构和反胶束进行了比较，基于两个标准：表面到表面的尺寸，以研究封闭的长度尺度的影响，和水与表面活性剂的比例，以研究水/界面相互作用。我们表明，水与表面活性剂的比例是主导因素的水与界面相互作用的性质，而不是特征纳米级的距离。界面的详细结构和水与界面之间的特定相互作用也对受表面影响的水分子的分数起着关键作用。一个双组分模型，其中水被分离成散装状的水在中心的层状结构或反胶束和界面水是用来定量提取的界面动力学。与反胶束相比，由于每个AOT分子的较大表面积和水分子通过层状结构中的磺酸盐头部基团的更大渗透，更大数量的扰动水分子存在于层状结构中。
To determine the relative importance of the confining geometry and nanoscopic length scale versus water/interface interactions, the dynamic interactions between water and interfaces are studied with ultrafast infrared spectroscopy. Aerosol OT (AOT) is a surfactant that can form two-dimensional lamellar structures with known water layer thickness as well as well-defined monodispersed spherical reverse micelles of known water nanopool diameter. Lamellar structures and reverse micelles are compared based on two criteria: surface-to-surface dimensions to study the effect of confining length scales, and water-to-surfactant ratio to study water/interface interactions. We show that the water-to-surfactant ratio is the dominant factor governing the nature of water interacting with an interface, not the characteristic nanoscopic distance. The detailed structure of the interface and the specific interactions between water and the interface also play a critical role in the fraction of water molecules influenced by the surface. A two-component model in which water is separated into bulk-like water in the center of the lamellar structure or reverse micelle and interfacial water is used to quantitatively extract the interfacial dynamics. A greater number of perturbed water molecules are present in the lamellar structures as compared to the reverse micelles due to the larger surface area per AOT molecule and the greater penetration of water molecules past the sulfonate head groups in the lamellar structures.