Pacific Northwest National Laboratory, PO Box 999, Richland, Washington 99352, USA.
Langmuir. 2012 May 8;28(18):7182-8. doi: 10.1021/la204322k. Epub 2012 Mar 8.
The use of air-water, θ(wa), or air-liquid contact angles is customary in surface science, while oil-water contact angles, θ(ow), are of paramount importance in subsurface multiphase flow phenomena including petroleum recovery, nonaqueous phase liquid fate and transport, and geological carbon sequestration. In this paper we determine both the air-water and oil-water contact angles of silica surfaces modified with a diverse selection of silanes, using hexadecane as the oil. The silanes included alkylsilanes, alkylarylsilanes, and silanes with alkyl or aryl groups that are functionalized with heteroatoms such as N, O, and S. These silanes yielded surfaces with wettabilities from water wet to oil wet, including specific silanized surfaces functionalized with heteroatoms that yield intermediate wet surfaces. The oil-water contact angles for clean and silanized surfaces, excluding one partially fluorinated surface, correlate linearly with air-water contact angles with a slope of 1.41 (R = 0.981, n = 13). These data were used to examine a previously untested theoretical treatment relating air-water and oil-water contact angles in terms of fluid interfacial energies. Plotting the cosines of these contact angles against one another, we obtain the relationship cos θ(wa) = 0.667 cos θ(ow) + 0.384 (R = 0.981, n = 13), intercepting cos θ(ow) = -1 at -0.284, which is in excellent agreement with the linear assumption of the theory. The theoretical slope, based on the fluid interfacial tensions σ(wa), σ(ow), and σ(oa), is 0.67. We also demonstrate how silanes can be used to alter the wettability of the interior of a pore network micromodel device constructed in silicon/silica with a glass cover plate. Such micromodels are used to study multiphase flow phenomena. The contact angle of the resulting interior was determined in situ. An intermediate wet micromodel gave a contact angle in excellent agreement with that obtained on an open planar silica surface using the same silane.
在表面科学中，通常使用气-水（θ（wa））或气-液接触角，而油-水接触角（θ（ow））在包括石油回收、非水相液体命运和传输以及地质碳封存在内的地下多相流现象中至关重要。在本文中，我们使用十六烷作为油，确定了用各种硅烷修饰的二氧化硅表面的气-水和油-水接触角。硅烷包括烷基硅烷、芳基烷基硅烷以及具有用杂原子（如 N、O 和 S）官能化的烷基或芳基的硅烷。这些硅烷产生了从水湿到油湿的润湿性的表面，包括用杂原子官能化的特定硅烷化表面，这些表面产生了中间润湿的表面。清洁表面和硅烷化表面（不包括一个部分氟化表面）的油-水接触角与气-水接触角呈线性相关，斜率为 1.41（R = 0.981，n = 13）。这些数据用于检验一种以前未经测试的理论处理方法，该方法根据流体界面能来关联气-水和油-水接触角。将这些接触角的余弦相互绘制，我们得到了关系 cosθ（wa）= 0.667 cosθ（ow）+ 0.384（R = 0.981，n = 13），在 cosθ（ow）= -1 处截距为 -0.284，这与理论的线性假设非常吻合。基于流体界面张力σ（wa）、σ（ow）和σ（oa）的理论斜率为 0.67。我们还展示了如何使用硅烷来改变用玻璃盖板构建在硅/二氧化硅中的多孔网络微模型装置的内部润湿性。这种微模型用于研究多相流现象。原位确定了所得内部的接触角。具有中间润湿的微模型的接触角与在使用相同硅烷的开放平面二氧化硅表面上获得的接触角非常吻合。
