THE INFLUENCE OF SOLUTION pH ON THE ELECTROSYNTHESIS AND

I.L. LEHR; O.V. QUINZANI; S.B. SAIDMAN

Polypyrrole: Properties, Performance and Applications

Nova Science Publishers

Lugar: Nueva York; Año: 2011; p. 131 - 156

Polypyrrole (PPy) is considered as one of the best promising conducting polymers for a variety of applications including analytical devices, actuators and corrosion control coatings. In this chapter results are presented and discussed on the effects of solution pH on the electrosynthesis process of PPy and on the electrochemical behaviour of the formed films. The properties of the obtained polymers were investigated using electrochemical measurements, SEM/EDX and IR spectroscopy. The pH of the solution is an important parameter that strongly influences pyrrole polymerization. In the case of electrosynthesis onto oxidizable metals it should be also considered that the nature of surface oxide film is pH-dependent. Most of the studies devoted to the electrosynthesis of PPy have been carried out in organic or acid aqueous solution and there exists some controversy about the effects of high solution pH on the electropolymerization process. While it was reported that low pH values are essential for obtaining oxidative polymerization, several studies have been demonstrated that the polymer films could be deposited even in the presence of a strongly alkaline medium. The ion-exchange properties of the obtained PPy films are also dependent on the solution pH. It was reported that films generated in acid or neutral media were degraded in contact with basic solutions due to an irreversible loss of conjugation. On the contrary, the films synthesized in alkaline solutions can be cycled in acid or in basic media without loosing electrochemical activity. Then these coatings should be suitable materials for applications in alkaline solution, a medium which is preferred for several chemical reactions. The obtained results are explained by considering that the pH of the electropolymerization medium affects polymer chains organization.