Self-Assembly of Fatty Acids on Hydroxylated Al Surface and Effects of Their Stability on Wettability and Nanoscale Organization

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• 作者：Irma Liascukiene ; Marie Steffenhagen ; Svajus J. Asadauskas ; Jean-Fran莽ois Lambert ; Jessem Landoulsi
• 刊名：Langmuir
• 出版年：2014
• 出版时间：May 27, 2014
• 年：2014
• 卷：30
• 期：20
• 页码：5797-5807
• 全文大小：707K
• 年卷期：v.30,no.20(May 27, 2014)
• ISSN：1520-5827

文摘

The self-assembly of fatty acids (FA) on the surfaces of inorganic materials is a relevant way to control their wetting properties. While the mechanism of adsorption on model flat substrate is well described in the literature, interfacial processes remain poorly documented on nanostructured surfaces. In this study, we report the self-assembly of a variety of FA on a hydroxylated Al surface which exhibits a random nanoscale organization. Our results revealed a peculiar fingerprint due to the FA self-assembly which consists in the formation of aligned nanopatterns in a state of hierarchical nanostructuration, regardless of the molecular structure of the FA (chain length, level of unsaturation). After a significant removal of adsorbed FA using UV/O₃ treatment, a complete wetting was reached, and a noticeable disturbance of the surface morphology was observed, evidencing the pivotal role of FA molecules to maintain these nanostructures. The origin of wetting properties was investigated prior to and after conditioning of FA-modified samples taking into account key parameters, namely the surface roughness and its composition. For this purpose, the Wenzel roughness, defined as the third moment of power spectral density, was used, as it is sensitive to high spatial frequency and thus to the obtained hierarchical level of nanostructuration. Our results revealed that no correlation can be made between water contact angles (胃_w) and the Wenzel roughness. By contrast, 胃_w strongly increased with the amount of 鈭扖H_x鈥?groups exhibited by adsorbed FA. These findings suggest that the main origin of hydrophobization is the presence of self-assembled molecules and that the surface roughness has only a small contribution to the wettability.