Ranathunga Dineli T S, Shamir Alexandra, Dai Xianming, Nielsen Steven O
Department of Chemistry and Biochemistry, The University of Texas at Dallas, 800 West Campbell Road, Richardson, Texas 75080, United States.
Department of Mechanical Engineering, The University of Texas at Dallas, 800 West Campbell Road, Richardson, Texas 75080, United States.
Langmuir. 2020 Jul 7;36(26):7383-7391. doi: 10.1021/acs.langmuir.0c00915. Epub 2020 Jun 18.
Water condensation plays a major role in a wide range of industrial applications. Over the past few years, many studies have shown interest in designing surfaces with enhanced water condensation and removal properties. It is well known that heterogeneous nucleation outperforms homogeneous nucleation in the condensation process. Because heterogeneous nucleation initiates on a surface at a small scale, it is highly desirable to characterize water-surface interactions at the molecular level. Molecular dynamics (MD) simulations can provide direct insight into heterogeneous nucleation and advance surface designs. Existing MD simulations of water condensation on surfaces were conducted by tuning the solid-water van der Waals interaction energy as a substitute for modeling surfaces with different wettabilities. However, this approach cannot reflect the real intermolecular interactions between the surface and water molecules. Here, we report MD simulations of water condensation on realistic surfaces of alkanethiol self-assembled monolayers with different head group chemistries. We show that decreasing surface hydrophobicity significantly increases the electrostatic forces between water molecules and the surface, thus increasing the water condensation rate. We observe a strong correlation between our rate of condensation results and the results from other surface characterization metrics, such as the interfacial thermal conductance, contact angle, and the molecular-scale wettability metric of Garde and co-workers. This work provides insight into the water condensation process at the molecular scale on surfaces with tunable wettability.
水凝结在广泛的工业应用中起着重要作用。在过去几年里，许多研究都对设计具有增强的水凝结和去除特性的表面表现出兴趣。众所周知，在凝结过程中，异质成核优于同质成核。由于异质成核在小尺度的表面上启动，因此非常希望在分子水平上表征水与表面的相互作用。分子动力学（MD）模拟可以直接深入了解异质成核并推进表面设计。现有的关于表面上水凝结的MD模拟是通过调整固体与水的范德华相互作用能来进行替代模拟具有不同润湿性的表面。然而，这种方法无法反映表面与水分子之间真实的分子间相互作用。在这里，我们报告了在具有不同头基化学性质的烷硫醇自组装单分子层的实际表面上水凝结的MD模拟。我们表明，降低表面疏水性会显著增加水分子与表面之间的静电力，从而提高水的凝结速率。我们观察到我们的凝结速率结果与其他表面表征指标的结果之间存在很强的相关性，例如界面热导率、接触角以及加德及其同事的分子尺度润湿性指标。这项工作为在具有可调润湿性的表面上分子尺度的水凝结过程提供了深入见解。
