| Abstract [eng] |
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. Investigation of the mechanism of self-assembly of fatty acids (FA) and methyl oleate on an Al oxy-hydroxide surface was done. After the FA adsorption, the presence of coordinative bonded carboxylate species on the Al oxy-hydroxide surface is demonstrated by means of PM-IRRAS analysis. The contact of methyl oleate with the surface leads to its chemical transformation through a saponification-hydrolysis reaction. As a consequence, it binds to the surface in a manner similar to that for fatty acids. AFM demonstrated the change of morphology - the existence of highly ordered nanostructures, the formation of aligned nano-patterns, guided only by the FA self-assembly. The stability and the origin of wetting properties of the self-assembled layers was examined under UV/O3 treatment, in air and in aqueous media taking into account key parameters, namely the surface roughness and its composition. Results revealed that no correlation can be made between water contact angles and the Wenzel roughness. By contrast, water contact angle strongly increased with the amount of -CHx- groups exhibited by adsorbed FA. These findings suggest that the main origin of hydrophobisation is the presence of self-assembled molecules and that the surface roughness has only a small contribution to the wettability. Phospholipid (DPPC) was adsorbed on both hydrophilic AlOOH and hydrophobic SA-AlOOH surfaces. With increasing the concentration of DPPC in solution, the adsorbed phase may include multiple (bi)layers which seems to remain stable upon hydration and could be used for tuning surface properties (especially wettability) and interaction with different environment. |
