Detection of the hydrophobic surface force in foam films by measurements of the critical thickness of the film rupture
Detection of the hydrophobic surface force in foam films by measurements of the critical thickness of the film rupture
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DOI：
10.1021/la0357514
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发表时间：
2004-03-02
期刊：
影响因子：
3.9
通讯作者：
Lips, A
中科院分区：
文献类型：
--
作者：
Angarska, JK;Dimitrova, BS;Lips, A
在足够高的电解质浓度下（在抑制静电排斥下），自由泡沫膜逐渐变薄，直到达到一定的临界厚度，然后它们破裂。该临界厚度的值对作用在膜中的吸引表面力的大小敏感。我们实验研究了破裂的膜形成的十二烷基硫酸钠（SDS）的水溶液中加入0.3 M NaCl的存在下。理论拟合的数据表明，货车德瓦尔斯相互作用，单独，是不足以解释测得的临界厚度，特别是对于较低的SDS浓度。如果这种差异归因于疏水吸引，那么理论和实验之间达到了很好的一致。从最佳拟合，我们确定的疏水力的衰减长度约为15.8 nm，这与其他作者获得的疏水化云母表面的值相一致。疏水相互作用的强度随着SDS浓度的降低而增加，这可以用以下事实来解释：在吸附的表面活性剂分子之间，暴露出更大面积的裸露的疏水空气-水界面。在研究的浓度范围内，疏水力的强度被发现是成反比的表面密度的吸附离子。
At sufficiently high electrolyte concentrations (at suppressed electrostatic repulsion), the free foam films thin gradually, until reaching a certain critical thickness, and then they break. The value of this critical thickness is sensitive to the magnitude of the attractive surface forces acting in the film. We experimentally investigated the rupture of the films formed from aqueous solutions of sodium dodecyl sulfate (SDS) in the presence of 0.3 M NaCl added. The theoretical fits of the data indicate that the van der Waals interaction, alone, is insufficient to explain the measured critical thickness, especially for the lower SDS concentrations. If the difference is attributed to the hydrophobic attraction, then a very good agreement between the theory and experiment is achieved. From the best fit, we determine that the decay length of the hydrophobic force is about 15.8 nm, which coincides with the value obtained by other authors for hydrophobized mica surfaces. The strength of the hydrophobic interaction increases with the decrease of the SDS concentration, which can be explained with the fact that between the adsorbed surfactant molecules greater areas of bare hydrophobic air-water interface are uncovered. In the investigated concentration range, the strength of the hydrophobic force is found to be inversely proportional to the surface density of the adsorbed ions.