Materials Physics, Department of Physics and Astronomy, Ångström Laboratory, Uppsala University, Box 516, 751 20, Uppsala, Sweden.
Langmuir. 2011 Apr 19;27(8):4669-78. doi: 10.1021/la1048985. Epub 2011 Mar 28.
The adsorption of sodium bis 2-ethylhexyl sulfosuccinate, NaAOT, to a sapphire surface from aqueous solution has been studied by neutron reflection at concentrations above the critical micelle concentration (cmc). Complementary measurements of the bulk structure were made with small-angle neutron scattering and grazing incidence small-angle neutron scattering. At a concentration of about 1% wt (10 × cmc), lamellar phase NaAOT was observed both at the surface and in the bulk. The structure seen at the interface for a solution of 2% wt NaAOT is a 35 ± 2 Å thick bilayer adsorbed to the sapphire surface at maximum packing density, followed by an aligned stack of fluctuating bilayers of thickness 51 ± 2 Å and with an area per molecule of 40 ± 2 Å(2). Each bilayer is separated by a water: at 25 °C, this layer is 148 ± 2 Å. A simple model for the reflectivity from fluctuating layers is presented, and for 2.0% wt NaAOT the fluctuations were found to have an amplitude of 25 ± 5 Å. The temperature sensitivity of the structure at the surface was investigated in the range 15-30 °C. The effect of temperature was pronounced, with the solvent layer becoming thinner and the volume occupied by the NaAOT molecules in a bilayer increasing with temperature. The amplitude of the fluctuations, however, is approximately temperature independent in this range. The adsorption of NaAOT at the sapphire surface resembles that previously found at hydrophilic and hydrophobic silica surfaces. The coexisting bulk lamellar phase has a spacing of layers similar to that observed at the surface. These observations are an indication that the major driving force for adsorption is self-assembly, independent of the chemical nature of the interface.
从水溶液中研究了二（2-乙基己基）磺基琥珀酸钠（NaAOT）在蓝宝石表面上的吸附，浓度高于临界胶束浓度（cmc）。使用小角中子散射和掠入射小角中子散射对体相结构进行了补充测量。在浓度约为 1%wt（10×cmc）时，在表面和体相都观察到了层状相 NaAOT。对于 2%wt NaAOT 溶液在界面上看到的结构是一个 35±2Å 厚的双层，在最大堆积密度下吸附在蓝宝石表面上，然后是一个对齐的波动双层堆栈，厚度为 51±2Å，每个双层之间有一个水分子层：在 25°C 时，这个层的厚度为 148±2Å。提出了一个用于波动层反射的简单模型，对于 2.0%wt NaAOT，发现波动的幅度为 25±5Å。在 15-30°C 的范围内研究了表面结构的温度敏感性。温度的影响很明显，溶剂层变得更薄，双层中 NaAOT 分子的体积随着温度的升高而增加。然而，在这个范围内，波动的幅度大致与温度无关。NaAOT 在蓝宝石表面上的吸附类似于以前在亲水和疏水二氧化硅表面上发现的吸附。共存的体相层状相的层间距与在表面上观察到的相似。这些观察结果表明，吸附的主要驱动力是自组装，而与界面的化学性质无关。
