Good adhesion between chemically oxidized titanium and electrochemically deposited polypyrrole

• A method for producing extremely adhesive polypyrrole (Ppy) films is described. The electrochemical synthesis of Ppy on thin chemically pre-oxidized Ti layers produces a mechanically strong, shiny polymer film with extremely good adhesion. Adhesion of Ppy films on Ti metal without chemical pre-oxidation is very weak. Two multilayer systems are described with Ppy as an electrochemically active layer, chemically oxidized Ti (TixOy) as a thin adhesive layer, and either a Si-wafer or Al foil as a substrate. Ppy films survive more than 6000 reduction-oxidation cycles in aqueous electrolyte without delamination. The possible mechanisms of enhanced adhesion are discussed. Those are: (1) increased adhesion due to changes in the chemical composition and surface structure of the pre-oxidized Ti, (2) the possibility of the chemical oxidation of pyrrole on the metal surface in addition to the electrochemical polymerization, (3) the adsorption of pyrrole molecules onto pre-oxidized Ti surface by interaction with Ti hydroxides on surface, and (4) the simultaneous growth of TixOy and Ppy.

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