COMPARISON OF THE ELECTRICAL PROPERTIES OF CONJUGATED AND PIGMENT POLYMER SYSTEMS

Abstract

SUMMARY : The work described in this thesis is concerned with an investigation of the electrical conductivity of polymers in which conductivity involves either a conjugated polymer backbone (polypyrrole para-toluene sulfonate) or carbon black filled polymers (polystyrene and polychloroprene). The study presented on polypyrrole para-toluene sulfonate was carried out to establish how variations in the electrochemical preparation affect the conductivity of the films produced. It was found that changes in the electrical conductivity of polypyrrole para-toluene sulfonate can be obtained by variations in the voltage and concentration of electrolyte used in the film synthesis. There is also a close correlation between the conductivity, growth rate, and the voltage used in the film preparation. It was found that the temperature dependence of the conductivity follows a typical cox-exp[-(T/T)1/4] law. The experimental results are analyzed within the framework of Mott's model for a variable-range hopping process, and it was observed that the model predicts the correct qualitative behavior for the conductivity The study presented on carbon black composites was carried out in an attempt to establish the influence of the matrix on the concentrating conductivity relationship in composite systems. It was found that the addition of carbon black to polychloroprene can lead to the creation of filler-polymer interactions that influence the molecular relaxation processes as well as the conductivity of the carbon black composites Similar observations were made on polystyrene carbon black com-posites. The conductivity-frequency dependence indicates that the con-ductivity follows typically (w)ocws law and the carrier movement could be ascribed to a “hopping mechanism”. The conductivity-frequency independence indicates that the conductivity does not follow a typical σ(w)ocw law. The conductivity decays with frequency and reaches a limiting value which does not decay further with frequency. This is indicative of the bulk conduction saturation. S