Zhang Ziyang, Wang Wenli, Korpacz Alexander N, Dufour Claudia R, Weiland Zachary J, Lambert Christopher R, Timko Michael T
Langmuir. 2019 Sep 24;35(38):12317-12325. doi: 10.1021/acs.langmuir.9b01252. Epub 2019 Sep 11.
Surface free energy remains a fundamental material property to characterize the interfacial interactions between liquid and solid. Here, we developed a precise approach to determine surface energy by using contact angles of binary mixtures of water-dimethyl sulfoxide (DMSO), water-formamide, water-ethylene glycol, and water-glycerol and analyzed using the Owens-Wendt method. A mixing equation was developed to estimate liquid-dispersive surface tension (γ) and polar surface tension (γ) parameters for binary mixtures. To test the approach, two hydrophobic surfaces, flat polydimethylsiloxane (PDMS), and silane-derivatized glass were prepared and the contact angle of mixtures on the surfaces were obtained. Surface energy of PDMS determined by three binary mixtures agrees with that from pure solvents, but the uncertainty decreases to less than 13%; remarkably, the uncertainty drops to around 5% once we combined measured contact angles from all the mixtures, namely, water-DMSO, water-formamide, and water-ethylene glycol. Surface energies of silane-derivatized glass bearing ethyl (C), hexyl (C), and octadecyl (C) alkyl chains were determined with water-formamide and water-glycerol mixtures. Measured contact angles fit the Owens-Wendt model, and surface energy value determined from different binary mixtures agree with each other within error. Contact angle measurement of liquid mixtures is a simple method for determination of surface energy that improves the precision of surface energy determined by measurements of multiple pure solvents.
表面自由能仍然是表征液体与固体之间界面相互作用的一种基本材料特性。在此，我们开发了一种精确方法，通过使用水 - 二甲基亚砜（DMSO）、水 - 甲酰胺、水 - 乙二醇和水 - 甘油二元混合物的接触角来测定表面能，并使用欧文斯 - 温德特方法进行分析。我们开发了一个混合方程来估算二元混合物的液体分散表面张力（γ）和极性表面张力（γ）参数。为了测试该方法，制备了两个疏水表面，即平整的聚二甲基硅氧烷（PDMS）和硅烷衍生化玻璃，并获得了混合物在这些表面上的接触角。由三种二元混合物测定的PDMS表面能与纯溶剂测定的结果一致，但不确定度降至小于13%；值得注意的是，一旦我们将所有混合物（即水 - DMSO、水 - 甲酰胺和水 - 乙二醇）测得的接触角结合起来，不确定度降至约5%。用水 - 甲酰胺和水 - 甘油混合物测定了带有乙基（C）、己基（C）和十八烷基（C）烷基链的硅烷衍生化玻璃的表面能。测得的接触角符合欧文斯 - 温德特模型，并且由不同二元混合物测定的表面能值在误差范围内相互一致。液体混合物的接触角测量是一种测定表面能的简单方法，它提高了通过多种纯溶剂测量所确定的表面能的精度。
