In the "brush model" of polymer modified electrodes it is assumed that the polymer film consists of short and long polymer chains forming bundles in such a way that only a small part of the metal substrate surface is covered by the polymeric material. The results of electrochemical impedance spectroscopy, cyclic voltammetry and surface stress measurements confirm that a brush-like ordering of the polymer chains on the metal surface is a realistic description of the surface film structure. Physicochemical parameters obtained from electrochemical impedance spectra for poly (o-phenylenediamine) films on platinum in contact with 1 M HClO4 or 0.5 M H2SO4 solution were analyzed on the basis of the brush model. The characteristic parameters derived from the impedance spectra of different electrodes were compared. (c) 2005 Elsevier Ltd. All rights reserved.