SPECTROSCOPIC ELLIPSOMETRY INVESTIGATION OF THE REDOX PROCESS OF POLYPYRROLE IN SEVERAL AQUEOUS-SOLUTIONS

In this work, the properties of polypyrrole films electrochemically gr own on platinum substrates from different aqueous solutions were studi ed using a spectroscopic ellipsometry technique at several electrode p otentials. The electrolytes were: NaCl 0.5 M, CsCl 0.5 M, Na2SO4 0.5 M with pH = 4.5, and H2SO4 0.5 M (pH = 0.4). In all electrolytes with p H 4.5, for electrode potentials above 0.0 V vs. SCE, the polymer chain s are in the highest state of oxidation, indicating that polarons are not present to a large extent. In a more acidic electrolyte, the film properties and oxidation mechanism are different from those under high er pH conditions. In all electrolytes, there is an increase in the thi ckness and degree of hydration of the film with polymer oxidation. (C) 1998 Elsevier Science B.V. All rights reserved.