Abstract This paper presents a theoretical model based on molecular dynamics to represent and explain the experimental measurements of water droplet contact angles on fluorocarbon and hydrocarbon organosilicon surfactants of different chain lengths. In addition to the contact angles, we evaluated the distribution of the surfactants on the surface (surface density, packing degree, density profile, and coating thickness) and the interaction energies (surfactant–surfactant, surfactant–water, and water–water) to better understand the effect generated by the differences in the molecular structure of the surfactants. We found that the surface densities of the fluorocarbon surfactants were lower than those of hydrocarbon surfactants. This is because fluorocarbon chains are more rigid and because the attractive interaction energy between CF chains is less than that between CH chains because the fluorine–fluorine repulsive electrostatic interactions are stronger than the corresponding hydrogen–hydrogen interactions. The wettability alteration resulted from the modified surface–water interactions. The initial state was hydrophilic (water angle contact of 24°), produced by the high interaction energy between water and the silica surface. Upon application of surfactant, the surface–water interaction energies were considerably lowered, generating hydrophobic surfaces, with water angles contact between 87° and 99°.

中文翻译：

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用于润湿性改变的碳氟化合物与碳氢有机硅表面活性剂：分子动力学方法

摘要 本文提出了一个基于分子动力学的理论模型来表示和解释不同链长碳氟化合物和烃类有机硅表面活性剂的水滴接触角的实验测量。除了接触角，我们还评估了表面活性剂在表面的分布（表面密度、堆积度、密度分布和涂层厚度）和相互作用能（表面活性剂-表面活性剂、表面活性剂-水和水-水）更好地了解表面活性剂分子结构差异所产生的影响。我们发现氟碳表面活性剂的表面密度低于碳氢表面活性剂的表面密度。这是因为碳氟链更刚性，并且因为 CF 链之间的吸引力相互作用能小于 CH 链之间的吸引力，因为氟 - 氟排斥静电相互作用比相应的氢 - 氢相互作用强。润湿性的改变是由于表面-水相互作用的改变造成的。初始状态是亲水的（水接触角为 24°），由水和二氧化硅表面之间的高相互作用能产生。应用表面活性剂后，表面-水相互作用能显着降低，产生疏水表面，水角接触在 87° 和 99° 之间。润湿性的改变是由于表面-水相互作用的改变造成的。初始状态是亲水的（水接触角为 24°），由水和二氧化硅表面之间的高相互作用能产生。应用表面活性剂后，表面-水相互作用能显着降低，产生疏水表面，水角接触在 87° 和 99° 之间。润湿性的改变是由于表面-水相互作用的改变造成的。初始状态是亲水的（水接触角为 24°），由水和二氧化硅表面之间的高相互作用能产生。应用表面活性剂后，表面-水相互作用能显着降低，产生疏水表面，水角接触在 87° 和 99° 之间。