Doctoral Dissertations

Date of Award

3-1988

Degree Type

Dissertation

Degree Name

Doctor of Philosophy

Major

Chemistry

Major Professor

J. Q. Chambers

Committee Members

G. Mamantov, C. A. Lane, K. J. Monty

Abstract

Polymer modification of electrode surfaces has been a topic of great interest in the past few years. Deliberate chemical modification of electrode surfaces has been used to suppress photocorrosion of semiconductor electrodes, electrocatalyze the conversion of light to energy, improve fuel cell performance, and sense specific ions in complex biological matrices. In our laboratory, different electrochemistry has been observed for polymer modified electrodes(PMEs) by varying the nature of the polymer backbone, the redox moiety itself, the concentration of the redox sites, film thickness, temperature, the supporting electrolyte, and the solvent.

This research studied the effects of temperature, supporting electrolyte, and solvent on PME electrochemistry by comparing cyclic voltammetric results to two PME, electrochemical models. Cyclic voltammetry and chronoamperometry were automated by interfacing an Apple II+, 6502-based, microcomputer to a Bioanalytical Systems GV-27 potentiostat with Interactive Structures A/D and D/A converters. Real-time data acquisition software was written in 6502 assembly language; file management, data reduction, and numerical analysis software was written in UCSD Pascal. Application of the electrochemical models to the digitally acquired data was facilitated by the Pascal programming environment. In addition to useful electrochemical information, conclusions were drawn from the microcomputer interface and programming design to evaluate the potential of other microcomputers and high-level programming languages to electrochemical methods.

Both models suggest that mechanical effects in PMEs arising from the forced intrusion of charge compensating counterion and solvent during oxidation or reduction should be included in the electrochemical theory. Elasticity changes in thin films of a tetracyanoquinodimethane terpolymer and poly(vinylferrocene) were observed as the temperature, supporting electrolyte, and solvent were varied. Neither model alone explained the electrochemical results. The concepts of stress-strain and measurement time invoked in the mechanical/electrochemical model explained the interaction parameter results. The results indicated that solvent-polymer interactions neglected in the mechanical/electrochemical model should be included in the derivation and that polymer elasticity as a function of these three variables should be included among the factors influencing charge transport through thin polymer films.

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