Abstract
The ac response of polyaniline films on Pt electrodes in 
was measured at different applied dc potentials, varied in the positive and negative directions. Experimental complex capacitance plots were reproduced using a computer simulation program based upon the equivalent circuit approach. With 150 nm films the complex capacitance plots at +0.55V (vs. SCE) comprise a single capacitive element, which develops at more negative potentials into a parallel combination of two discrete elements 
(a capacitor) and 
(a finite transmission line) in series with a polymer resistance 
. 
and 
are interpreted as double‐layer and faradaic (diffusion‐controlled) components. The hysteresis observed in the voltammetric behavior of polyaniline is evident in the potential‐dependence of 
, 
, and 
, obtained under constant‐potential conditions.