State Key Laboratory of Electrical Insulation and Power Equipment, Xi'an Jiaotong University, Xi'an, Shaanxi 710049, People's Republic of China.
Langmuir. 2022 Dec 13;38(49):15353-15360. doi: 10.1021/acs.langmuir.2c02571. Epub 2022 Dec 1.
The wetting property of a solid surface has been a hotspot for centuries, and many studies suggest that the hydrophobicity is highly related to the polar components. However, the underlying mechanism of polar moieties on the hydrophobicity remains unclear. Here, we tailor the surface polar moieties of epoxy resin (EP) by ozone modification and assess their wetting properties. Our results show that, for the modified EP with more (60.54%) polar moieties, the polar effect on hydrophobicity cannot be empirically observed. To reveal the underlying mechanism, the absorption parameters, including equilibrium distance, adsorption radius, and effective adsorption sites for water on EP before and after ozone treatment, are calculated on the basis of molecular simulations. After ozone modification, the equilibrium distance (from 1.95 to 1.70 Å), adsorption radius (from 3.80 to 4.50 Å), and effective adsorption sites (from 1 to 2) change slightly and the EP surface remains hydrophobic, although the polar groups significantly increase. Therefore, it is concluded that the wetting properties of solid surfaces are dominated by the equilibrium distance, adsorption radius, and effective adsorption sites for water on solids, and the nonlinear relationship between polar groups and hydrophilicity is clarified.
固体表面的润湿性是几个世纪以来的研究热点，许多研究表明疏水性与极性成分高度相关。然而，极性基团对疏水性的潜在机制仍不清楚。在这里，我们通过臭氧修饰来调整环氧树脂（EP）的表面极性基团，并评估其润湿性。结果表明，对于具有更多（60.54%）极性基团的改性 EP，极性对疏水性的影响无法从经验上观察到。为了揭示潜在的机制，我们基于分子模拟计算了 EP 在臭氧处理前后的吸收参数，包括水在 EP 上的平衡距离、吸附半径和有效吸附位。臭氧修饰后，平衡距离（从 1.95 到 1.70Å）、吸附半径（从 3.80 到 4.50Å）和有效吸附位（从 1 到 2）略有变化，EP 表面仍然疏水，尽管极性基团显著增加。因此，可以得出结论，固体表面的润湿性主要由固体上水的平衡距离、吸附半径和有效吸附位决定，澄清了极性基团与亲水性之间的非线性关系。
