Wettability is an important parameter of micro/nanostructured composites. The measurement of apparent contact angle is strongly affected by surface roughness, which induces some challenges to study the intrinsic hydrophobicity correlating to the nature of chemistry. Carbon-Nafion composites exhibited about 30° decrease in apparent contact angle from 30 to 10°C due to the condensation of water vapor into cavities, suggesting a significant Cassie–Wenzel wetting transition phenomenon. The focus of this work has been on the first-time use of a low-T Cassie–Wenzel wetting transition method to evaluate Young's (ideal) contact angle and surface free energy. A maximum Young's contact angle (113°) and minimum total surface energy (12 mJ/m²) were determined at Nafion content of 70 wt%, indicating the orientation effect that sulfonate groups in Nafion preferentially pointed toward polar carbon. This approach provided the reasonable prediction of intrinsic hydrophobicity, especially when a rough solid surface is not easily wetted by liquids.

中文翻译：

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通过低 T Cassie-Wenzel 润湿转变方法调整粗糙表面的固有疏水性和表面能

润湿性是微/纳米结构复合材料的一个重要参数。表观接触角的测量受表面粗糙度的强烈影响，这对研究与化学性质相关的固有疏水性提出了一些挑战。由于水蒸气凝结到空腔中，Carbon-Nafion 复合材料的表观接触角从 30°C 降低了约 30°C，表明存在显着的 Cassie-Wenzel 润湿转变现象。这项工作的重点是首次使用低 T Cassie-Wenzel 润湿转变方法来评估杨氏（理想）接触角和表面自由能。最大杨氏接触角 (113°) 和最小总表面能 (12 mJ/m ²) 是在 Nafion 含量为 70 wt% 时测定的，表明 Nafion 中的磺酸基团优先指向极性碳的取向效应。这种方法提供了对固有疏水性的合理预测，尤其是当粗糙的固体表面不易被液体润湿时。