Year

1994

Degree Name

Doctor of Philosophy

Department

Department of Materials Engineering

Abstract

One of the problems limiting the application of conducting polymers as commercial materials has been the lack of solubility in most common solvents. An alternative approach might be the preparation of sterically stabilized conducting polymer colloids via dispersion polymerization.

In general the oxidation of pyrrole and aniline is carried out in the presence of a steric stabilizer to produce a colloidal dispersion. In this work various stabilizers such as PVP, PVA, and PEO were used for colloid formation. The preparation, characterization and electrical properties of polypyrrole and polyaniline colloids have been studied. It was found that type and concentration of stabilizer affects the morphology, electroactivity, conductivity and yield of polymer. Electrocoagulation of colloids onto various substrates was considered.

The electrochemical oxidation/polymerization of pyrrole and aniline monomer in the presence of steric stabilizers (PVP, PVA, PEO) and the properties of the resultant polymers was also investigated. Various techniques such as galvanostatic oxidation (constant current), potentiostatic oxidation (constant potential), and potentiodynamic (potential ramp) oxidation were used to initiate this process. It was found that the type and concentration of stabilizer affects the rate of polymerization as well as the electroactivity and morphology of the resultant colloidal sol. It was found that the rate of polymerization and the electroactivity decreased with increased concentration of stabilizer.

The effect of rotation rate, type of stabilizer and stabilizer concentration on the rate of polymerization were studied. The results indicated that rate of polymerization/deposition decreased with increased electrode rotation rate and with stabilizer concentration. For the first time the use of electropolymerization in the presence of the steric stabilizers with various counterions in order to produce conducting polymer colloids has been investigated. The colloids produced are sterically stable and are electroactive.

Applications for conductive polymer colloids were considered. For example, the preparation of conductive electroactive paints has been investigated using polypyrrole and polyaniline colloids mixed with standard acrylic paints. The electroactivity, conductivity and adhesive strength of the resultant paints was investigated.

The use of colloids for the development of novel conductive polymer composites was studied. The electrodeposition of mixtures of polypyrrole and polyaniline colloids, polyaniline colloids and pyrrole monomer or polyaniline colloids with polystyrene sulphonate particles was investigated.

Thermal degradation of polyethylene in the presence of colloidal polypyrrole and polyaniline was investigated. The results indicated that polypyrrole and polyaniline colloids might be used as a stabilizing additive to prevent the thermal degradation of polyethylene.

This study indicated that conducting polymer colloids can be prepared both chemically and electrochemically and these colloids can be used for various applications.

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