Clay montmorillonite derivatized electrode as a template for electrosynthesis of conducting polymers and organic biomolecules

Abstract

In this thesis the electrochemical studies of a special type of polymers namely conducting polymers (CPs) using cyclic voltammetry technique is reported. This is a fast electroanalytical tool capable of providing qualitative and quantitative information about electron transfer kinetics and probing the subsequent chemical reactions. The CPs of interest are polyaniline, polypyrrole, polynaphthol and polythiophene. Electrodeposition of the CPs on both carbon and clay modified electrode surface is described. The carbon graphite working electrode surface was modified/or derivatized using a clay montmorillonite-bentonite. The elemental composition of the modification material was obtained from x-ray fluorescence (XRF) analysis. Results obtained on derivitization of the working electrode surface with clay montmorillonite treated with varying amounts of acid are presented. The resultant changes in the population of Bronsted and Lewis acid sites is shown to affect the redox properties of a conducting polymer, polyaniline. The experimental observations are explained in terms of structural modification of clays on treatment with acid. The electron transfer process in polyaniline electrodeposited on various acidified clay modified electrodes fitted to the Allen-Hickling equation for quasi-reversible redox systems reveal that the electron transfer coefficients decrease (range from 0.642 to 0.171) as the films become thicker signifying the poor efficiency of electron transfer in thick films.