Year

1994

Degree Name

Doctor of Philosophy

Department

Department of Chemistry

Abstract

In this project two different resistometric strategies, DC and pulse resistometry, have been employed. Both DC and pulse resistometry can be used to monitor changes in resistance of conducting polymers as a function of applied potential. Care should be taken in any quantitative comparison of the measurements obtained, since the technique used for resistance measurements are not identical. However, it can be said that the DC resistometry method is capable of providing data on the rate of change of resistance as a function of applied potential more sensitively than the pulse method. In contrast, the pulse method is more applicable over a wider potential range.

The switching properties of conducting polymers are critical to numerous applications. The resistance/potential (R/E) profiles obtained in this investigation, have been shown to be dependent on various parameters. These includes the nature of the monomer and counterion used, the method of growth and the nature of the electrolyte solution.

In this thesis, a new simultaneous analysis technique was also introduced by a combination of several simple methods. This technique denoted S.M.A.C. enables the relationship between charge transfer, mass changes and resistance changes to be determined simultaneously, in-situ and in 'real time'. Using this method the effect of the chaotropic nature of the cations used in the electrolyte solution on the R/E profile of conducting polymers was examined. It was found that the nature of the cation, while not obvious in cyclic voltammetry, has a marked effect on the changes in resistance and mass that occur within the polymer upon reduction/oxidation.

The effect of pH on the resistance of the polymer has also been studied. The DC technique was mainly used for pH detection studies in both the stationary and the flow system. Different polymeric sensing materials including PPy/Cl, PPy/PVS, PAn/Cl and PPy/PVS-PAn/Cl were employed. Interesting results were observed when PPy/PVS was used. In the flow system a new approach to the configuration and the shape of sensing material was applied using a "moving tape". The moving tape experimental results hold promise further investigation of pH detection.

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