CONCENTRATION-DRIVEN SURFACE TRANSITION IN THE WETTING OF MIXED ALKANETHIOL MONOLAYERS ON GOLD
CONCENTRATION-DRIVEN SURFACE TRANSITION IN THE WETTING OF MIXED ALKANETHIOL MONOLAYERS ON GOLD
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DOI：
10.1021/ja00005a004
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发表时间：
1991-02-27
影响因子：
15
通讯作者：
CHANG, JC
中科院分区：
文献类型：
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作者：
ULMAN, A;EVANS, SD;CHANG, JC
报道了含有疏水性和亲水性组分的混合单层的结构，其中三种不同液体的接触角随着单层组合物的高度非线性函数而变化。 这表明，由于表面化学势（“表面场”）增强，亲水表面附近存在可能由大量蒸汽形成的预润湿的晶体状水层。 随着亲水成分浓度的降低，表面场分布中“猝灭随机性”的增加破坏了表面冷凝水相，从而引发了所观察到的接触角的非线性。 通过连续蒙特卡罗模拟揭示了吸附在 OH 表面上的水分子的微观结构，具有真实的力场，并且该场景得到了简化晶格气体模型的平均场计算的支持。 当相对湿度小于或等于 2% 时，以及当通过向混合单层的疏水性（CH3 封端）组分添加两个 CH2 基团使单层表面分子粗糙化时，在 30% 相对湿度下观察到的润湿行为会发生变化。 有人认为，这种过渡现象是由于预润湿水层的形成而导致可能的（真实的或圆形的）表面相变。这种形成是由随机表面场的淬灭分布的变化触发的。
The construction of mixed monolayers containing hydrophobic and hydrophilic components for which the contact angles for three different liquids vary as a highly nonlinear function of the monolayer composition is reported. It is suggested that a prewetting, crystalline-like layer of water, possibly formed from bulk vapor, is present near the hydrophilic surface, because of an enhanced surface chemical potential (''surface field''). As the concentration of the hydrophilic component is lowered, increasing ''quenched randomness'' in the distribution of surface fields destroys the surface condensed water phase, thus triggering the observed nonlinearity in the contact angles. The microscopic structure of the water molecules adsorbed on an OH surface is revealed by continuum Monte Carlo simulations, with realistic force fields, and the scenario is supported by mean-field calculations on a simplified lattice-gas model. The observed wetting behavior at 30% relative humidity was altered for a relative humidity less-than-or-equal-to 2%, as well as when the surface of the monolayer was molecularly roughened by the addition of two CH2 groups to the hydrophobic (CH3-terminated) component of the mixed monolayers. It is suggested that this transitional phenomenon is due to a possible (true or rounded) surface phase transition, due to the formation of a prewetting water layer. This formation is triggered by variations in the quenched distribution of random surface fields.