Switching Reaction of Conductive Polymers: I. Models for Charge Transfer Control

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Abstract
The switching reaction of conductive polymers can be described as two simultaneous steps: the transfer of an electron to or from the conductive polymer and the diffusion of the counterion out of or into the polymer. The charge‐transfer‐controlled switching reaction is modeled by assuming it to be first order reversible or irreversible. The reactant is a polymer unit, charged or neutral, depending on the switching reaction. The charge capacity of the film is proportional to the charge passed during electropolymerization. The models depend primarily on three unknown parameters: anodic or cathodic transfer coefficient and two kinetic constants. Additional information required by the models include the number of electrons transferred during electropolymerization to add one monomer unit, the switching potential, and the fraction of anions per monomer unit. Both reversible and irreversible models are used to simulate cyclic voltammetric and chronocoulometric experiments. The simpler irreversible model is justified when the scan rate exceeds 0.01 V/s. The irreversible model predicts that the peak current is linearly proportional to the scan rate while the charge passed during the switching reaction is linearly proportional to time. Also, the peak current and the charge passed during the switching reaction are both linearly proportional to the charge passed during electropolymerization.

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