The intrinsic interfacial structure of ionic surfactant monolayers at water–oil and water–vapour interfaces
The intrinsic interfacial structure of ionic surfactant monolayers at water–oil and water–vapour interfaces
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水-油和水-蒸气界面离子表面活性剂单分子层的固有界面结构
DOI：
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发表时间：
2011
期刊：
影响因子：
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通讯作者：
F. Bresme
中科院分区：
文献类型：
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作者：
H. Martínez;E. Chacón;P. Tarazona;F. Bresme
利用计算机模拟研究了十二烷基硫酸钠（SDS）单层膜在水表面和水-油界面吸附的界面结构。利用去除毛细波平均效应的算法，我们获得了单分子层周围水的溶剂化结构的详细视图。我们研究了表面活性剂在45 ~ 33 Å2之间的表面浓度，这接近于实验条件下对应的临界胶束浓度和牛顿黑膜的形成。表面活性剂在水中形成层状结构，层状结构在离单层平面约1nm处消失。水分子表现出偶极子指向单分子层的优先取向。取向序衰减缓慢，但不影响水的氢键结构，仅在界面区域受到明显破坏。这些结构变化在sds -水和油- sds -水界面中是相同的。在后一种情况下，我们发现单层中有小程度的油渗透（每个SDS在0.2到0.25分子之间）。这种小的渗透对单层有可测量的影响，它增加了大约10%的厚度。SDS单层的弯曲模量是热能的数量级，kBT。
Using computer simulations, we investigate the interfacial structure of sodium dodecyl sulphate (SDS) monolayers adsorbed at the water surface and water–oil interfaces. Using an algorithm that removes the averaging effect of the capillary waves, we obtain a detailed view of the solvation structure of water around the monolayer. We investigate surface concentrations between 45 and 33 Å2 per surfactant, which are near experimental conditions corresponding to the critical micellar concentration and the formation of Newton black films. The surfactants induce a layering structure in water, which disappears at approximately 1 nm from the monolayer plane. The water molecules exhibit a preferred orientation with the dipoles pointing towards the monolayer. The orientational order decays slowly, but it does not influence the hydrogen bond structure of water, which is significantly disrupted in the interfacial region only. These structural changes are qualitatively the same in SDS–water and oil–SDS–water interfaces. In the latter case, we find a small degree of penetration of oil in the monolayer (between 0.2 and 0.25 molecules per SDS). This small penetration has a measurable effect on the monolayer, which increases its thickness by approximately 10 per cent. The bending modulus of the SDS monolayers is of the order of the thermal energy, kBT.
DOI：
10.1021/jp909219k
发表时间：
2010-02-11
期刊：
The journal of physical chemistry. B
影响因子：
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作者：
Willard AP;Chandler D
通讯作者：
Chandler D