Good adhesion between chemically oxidised 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-oxidised 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 oxidised 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-oxidised Ti; (2) the possibility of the chemical oxidation of pyrrole on the metal surface in addition to the electrochemical polymerisation; (3) the adsorption of pyrrole molecules onto pre-oxidised Ti surface by interaction with Ti hydroxides on surface; and (4) the simultaneous growth of TixOy and Ppy. (C) 2000 Elsevier Science Ltd. All rights reserved.