Vandecan Yves, Indekeu Joseph O
Instituut voor Theoretische Fysica, Katholieke Universiteit Leuven, Celestijnenlaan 200D, Leuven, Belgium.
J Chem Phys. 2008 Mar 14;128(10):104902. doi: 10.1063/1.2838183.
We perform a theoretical study of the three-phase contact line and the line tension in an adsorbed colloid-polymer mixture near a first-order wetting transition, employing an interface displacement model. We use a simple free-energy functional to describe a colloid-polymer mixture near a hard wall. The bulk phase behavior and the substrate-adsorbate interaction are modeled by the free-volume theory for ideal polymers. The large size of the colloidal particles and the suppression of the van der Waals interaction by optical matching of colloid and solvent justify the planar hard wall model for the substrate. Following the Fisher-Jin scheme, we derive from the free-energy functional an interface potential V(l) for these mixtures. For a particle diameter of 10-100 nm, the calculations indicate a line tension tau approximately 10(-12)-10(-13) N at room temperature. In view of the ultralow interfacial tension in colloid-polymer mixtures, gamma approximately 10(-7) Nm, this leads to a rather large characteristic length scale taugamma in the micrometer range for the three-phase contact zone width. In contrast with molecular fluids, this zone could be studied directly with optical techniques such as confocal scanning laser microscopy.
我们采用界面位移模型，对一阶润湿转变附近吸附的胶体 - 聚合物混合物中的三相接触线和线张力进行了理论研究。我们使用一个简单的自由能泛函来描述靠近硬壁的胶体 - 聚合物混合物。本体相行为和底物 - 吸附物相互作用通过理想聚合物的自由体积理论来建模。胶体颗粒的大尺寸以及通过胶体与溶剂的光学匹配对范德华相互作用的抑制，证明了底物的平面硬壁模型的合理性。遵循费舍尔 - 金方案，我们从自由能泛函中推导出这些混合物的界面势V(l)。对于直径为10 - 100 nm的颗粒，计算表明在室温下线张力τ约为10^(-12) - 10^(-13) N。鉴于胶体 - 聚合物混合物中极低的界面张力γ约为10^(-7) N/m，这导致三相接触区宽度在微米范围内有相当大的特征长度尺度τ/γ。与分子流体不同，这个区域可以直接用共聚焦扫描激光显微镜等光学技术进行研究。
