Doctoral Dissertations

Date of Award

12-1986

Degree Type

Dissertation

Degree Name

Doctor of Philosophy

Major

Chemistry

Major Professor

J. Q. Chambers

Committee Members

E. L. Wehry, S. Alexandratos, K. J. Monty

Abstract

The synthesis of a polyester is discussed which employs a mixture of the electroactive 2,5-bis(2'-hydroxyethoxy)-7,7,8,8, tetracyanoquinodimethane (TCNQ-diol) and electroinactive 1,1-bis(hydroxyethoxylbenzene (BOEB-diol) with stoichiometric amounts of adipyl chloride in dimethylacetamide via solution polycondensation at low temperature. The product of this polymerization is a terpolymer, which was characterized using electrochemical, rapid scanning spectrophotometric methods (uv-vis, IR), gel, permeation chromatography (GPC), and elemental analysis.

Charge transport through polymer films containing the TCNQ structure in the polymer chain and swollen with acetonitrile solvent was studied as a function of film composition. Variation of the film composition was achieved by synthesis of TCNQ terpolymer and by casting blended films of the TCNQ polyester and an isomorphic polyester containing a benzene ring in place of the TCNQ structure. Formation of uniform blends was indicated for the neutral polymers, but phase separation took place on repeated cycling of the films between the 0 and -1 oxidation states.

Redox center site-site interactions were probed by following dimer formation of the TCNQ-• radical anion and by the charge transport process as measured by chronocoulometric Cottrell slopes. Electron spin resonance and cyclic voltammetric data indicate that interchain, and not intrachain, interactions occur in the reduced films.

The charge transport rate in the region of the TCNQ-•/ TCNQ2- couple relative to the rates for the TCNQ/ TCNQ2-•/TCNQ-• region was found to be considerably retarded in films of the terpolymer and the blends.

The kinetics of the heterogeneous charge transfer step for the TCNQ-•/ TCNQ2- process was studied using cyclic voltammetry at various scan rates. Limitations of the technique are pointed out.

Effect of film composition on chronocoulometry was studied. In all regards the chronocoulometric and cyclic voltammetric results were consistent. The limiting charge accepted by the films, estimated by the approach to thin layer behavior and the charge obtained by integration of the cyclic voltammograms were in agreement (±10%).

The Cottrell slopes displayed a temperature dependence as expected for a thermally activated diffusional process. Activation energies for the "apparent charge transport diffusion coefficient" were obtained for TCNO polyester and blends.

Cyclic voltammetric and chronocoulometric studies of TCNQ polvester/PEG (PEG: polyethylene glycol) blend films on platinum electrodes and in contact with various combinations of solvent/electrolyte systems revealed further insight into the process of charge transport.

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