Ion transport and charge compensation in conducting polymers

Albertar, Abdulrahman (2012) Ion transport and charge compensation in conducting polymers. Doctoral (PhD) thesis, Memorial University of Newfoundland.

[English] PDF (Migrated (PDF/A Conversion) from original format: (application/pdf)) - Accepted Version Available under License - The author retains copyright ownership and moral rights in this thesis. Neither the thesis nor substantial extracts from it may be printed or otherwise reproduced without the author's permission. Download (65MB) [English] PDF - Accepted Version Available under License - The author retains copyright ownership and moral rights in this thesis. Neither the thesis nor substantial extracts from it may be printed or otherwise reproduced without the author's permission. (Original Version)

Abstract

The ion transport properties and the accompanied charge compensation mechanisms of electrochemically prepared conducting polymers have been investigated by cyclic voltammetry and impedance spectroscopy. The conducting polymers considered in this work are polypyrrole and polyfluorenone in which p-doping and n-doping were probed, respectively, in various electrolyte solutions. Both polymers were prepared by anodic coupling polymerization using various techniques: potentiodynamic, potentiostatic, and galvanostatic. Chemical modifications of the two polymers have been achieved under optimized conditions to obtain high quality, stability, and interesting electrochemical properties, such as charge capacity and electroactivity, of the deposited films. These modifications can facilitate the understanding of ion transport in conducting polymers in order to enhance their use in many potential applications, such as batteries, fuel cells, flexible displays, and other electrochemical devices. The surface morphology and elemental analysis for the polymer films were characterized by scanning electron microscopy and energy dispersive X-ray emission, respectively. -- The rate and mode of ion transport in conducting polymers have been controlled using dopant anions of various sizes and charges during film deposition. Cyclic voltammetry and impedance spectroscopy have been used to probe the mode of ion transport (anion or cation transport) using scan rate dependence and potential dependence, respectively. An enhanced anion transport rate was achieved using large univalent dopant anions, while an enhanced cation transport rate was achieved using a polyanion electrolyte during film deposition. Polypyrrole film modifications have been achieved chemically using various additives during film deposition and electrochemically by overoxidation at mild potentials before film degradation. Deactivation and reactivation of the polyfluorenone films were investigated by cyclic voltammetry in which deactivation was achieved for modified and unmodified films by continuous cycling during n-doping. However, reactivation of a deactivated film was only achieved following modification with a steric stabilizer, polyethylene glycol, by polarizing the film at positive potentials.

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