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Surfaces hétérogènes contrôlées et systèmes diphasiques bidimensionnels

Abstract : This thesis presents the elaboration and the characterisation of controlled heterogeneous surfaces in order to study the effect of the heterogeneities on the wetting properties. These surfaces are obtained by preparing Langmuir-Blodgett films with a mixture of two amphiphilic molecules. These molecules were chosen for their different wetting properties : the first one is a long chain fatty acid while the second one is a partially fluorinated surfactant. The mixed films are first characterised at the air-water interface (Langmuir monolayers). In order to determine the mixing behaviour of the two molecules, the mixed films were studied at different scales using several experimental techniques. The results show that a complete phase separation takes place over the whole range of molar fractions and whatever the surface pressure. Circular domains of the fatty acid are evidenced.
The mixed films are then transferred on solid substrate. In order to obtain well anchored films, the transfer parameters were adapted. The molecular arrangement in the films is determined using grazing incidence X-ray diffraction with two angles of incidence of the beam to change its penetration depth. We also used atomic force microscopy to obtain surface topography and to check on the absence of defects. In the same way as at the air-water interface, circular domains are visualised. These domains coexist with a continuous phase which presents a labyrinthine structure attributed to a molecular reorganisation during transfer.
Then, we obtain a system that appears well adapted to study the wetting properties of heterogeneous surfaces : the two molecules are completely phase-separated and each phase has different properties.
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Contributor : Vincent Dupres <>
Submitted on : Thursday, March 14, 2002 - 1:11:08 PM
Last modification on : Thursday, March 5, 2020 - 12:06:06 PM
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Vincent Dupres. Surfaces hétérogènes contrôlées et systèmes diphasiques bidimensionnels. Analyse de données, Statistiques et Probabilités [physics.data-an]. Université de Cergy Pontoise, 2001. Français. ⟨tel-00001210⟩

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