Confinement-induced phase transition and hysteresis in colloidal forces for surfactant layers on hydrophobic surfaces.
Confinement-induced phase transition and hysteresis in colloidal forces for surfactant layers on hydrophobic surfaces.
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DOI：
10.1021/la046947m
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发表时间：
2005-10
期刊：
影响因子：
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通讯作者：
L. Koopal;F. Leermakers;W. J. Lokar;W. Ducker
中科院分区：
文献类型：
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作者：
L. Koopal;F. Leermakers;W. J. Lokar;W. Ducker
在这篇文章中，我们考虑了界面附近的表面活性剂溶液。众所周知，表面活性剂分子之间强烈的侧向相互作用会引起吸附等温线的一个台阶。在自洽场理论中，吸附量的这一步表现为范德华循环。分析了这种回路对表面力实验的影响。从固定限制条件下的吸附等温线中，我们提取了固定化学势作为限制条件的函数的相应的吸附量。对于相互作用能与狭缝宽度之间的关系，发现了一种尖峰结构：存在限制诱导的一级相变。相应的相互作用曲线在双节点狭缝距离处有一个拐点。介绍了亚稳分支和不稳定分支(由两个旋节点包围)。在原子力显微镜或表面力仪器实验中，亚稳态可能会引起力滞后，这与由于悬臂系统的机械不稳定性而引起的结果截然不同。
In this paper we consider surfactant solutions near a pair of interfaces. It is well-known that strong lateral interactions between surfactant molecules give rise to a step in the adsorption isotherm. In a self-consistent field theory, such a step in the adsorbed amount shows up as a van der Waals loop. The consequence of such a loop for surface force experiments is analyzed. From adsorption isotherms at fixed confinement we extract the relevant adsorbed amounts for a fixed chemical potential as a function of the confinement. A cusped structure is found for the relation between the interaction energy and the slit width: there is a confinement-induced first-order phase transition. The corresponding interaction curve has a kink at the binodal slit distance. Metastable branches as well as an unstable branch (bracketed by the two spinodal points) are presented. The metastability is expected to give rise to force hysteresis in, e.g., atomic force microscope or surface force apparatus experiments, distinctly different from those due to mechanical instabilities of the cantilever system.