Elaboration de revêtements multifonctionnels sur des surfaces de zinc et de zinc-nickel

  • François Berger

    Student thesis: Doc typesDoctor of Sciences

    Abstract

    This thesis is included in the framework of chemical modification of surfaces by molecular assemblies in order to create different functional coatings with specific properties. The performed studies consist in the elaboration of self-assembled monolayers, of type Y-(CH2)n-SH, on highly oxidisable metallic deposits; more precisely zinc and zinc-nickel deposits. The use of these organothiol molecules imposes to maintain the metallic nature of the surface therefore an electrochemical reduction of surface is needed before the self-assembly process. In the framework of this thesis, an original process is performed. The surface modification is realized on freshly electrodeposited zinc or zinc-nickel coatings; these films being modified directly after electrodeposition. As a first step, the feasibility and the comprehension of organothiols grafting on zinc and zinc-nickel coatings have been investigated through the self-assembly of molecule such as n-dodecanethiol (H3C-(CH2)11-SH). Optimal grafting conditions have been determined to obtain organized monolayers having good qualities. Then, the formation of multilayer materials created from connectors of type Y-(CH2)n-SH where the final function Y is different from methyl group (-CH3) has been performed. The synthesis and the self-assembly of undec-10-ene-1-thiol (H2C=CH-(CH2)9-SH) on zinc allowed to emphasize the “adhesion promoter” nature of this molecule compared with polymer of type polydimethylsiloxane reacting with unsaturated final function. The use of a second molecule, HO-(CH2)11-SH, attests the possible diversity of self-assembly process. Indeed, the final function allowed the creation of molecular bilayer films by condensation with the reactive heads of trimethoxysilane molecules. By comparison, in the case of organophosphonic acids, an insertion reaction takes place with priority on the condensation. Identical studies with organothiols have been carried out on zinc-nickel deposits. The results for this type of coatings are similar to those obtained on zinc surfaces. Finally, a comparative study between the self-assembly and the electrografting has emphasized the molecular self-assembling of organothiols by the properties conferred to the surface.
    Date of Award17 Jun 2010
    Original languageFrench
    Awarding Institution
    • University of Namur
    SupervisorZineb Mekhalif (Supervisor), Cédric Volcke (Jury), Benoit Champagne (President), Joseph DELHALLE (Jury), Fabrice Lallemand (Jury) & Jean Crahay (Jury)

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