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    Electrochemical synthesis and characterisation of polypyrrole/chitosan films doped with molecular anions


    Moloney, Emer (2014) Electrochemical synthesis and characterisation of polypyrrole/chitosan films doped with molecular anions. PhD thesis, National University of Ireland Maynooth.

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    Abstract

    In this thesis, results are presented and discussed on the synthesis of polypyrrole-chitosan composite films. These films were investigated for the incorporation and release of methyl orange (a model anionic dopant), dexamethasone (an anti-inflammatory drug) and oxacillin (an antibiotic). All drug-doped films were grown at a constant potential of 0.80 V vs SCE until a charge density of 0.25 C cm-2 was achieved. Initially, a novel approach was developed to prepare the polypyrrole-chitosan composite films by electrochemically polymerising pyrrole in a chitosan hydrogel network directly on an electrode surface. The electrochemical properties of the chitosan and the polypyrrole films differ, however the properties of polypyrrole are not adversely affected by the presence of chitosan, and it appears that the chitosan provides some mechanical reinforcement to the composite. A second approach was investigated and in this case, chitosan was cast on to the doped polypyrrole post electropolymerisation and then cured under an infrared lamp. This was found to be more suitable for incorporating larger anionic species. A comprehensive electrochemical characterisation of the polypyrrole-chitosan composite films was obtained using cyclic voltammetry and electrochemical impedance spectroscopy. The redox peaks were identified and explained in terms of anion transport for the polypyrrole-chloride films and cation transport for polypyrrole-methyl orange films. Electrochemical impedance data were fitted to equivalent circuits and the charge transfer resistance, the double-layer capacitance, charge-storage capacitance, and conductivity were determined. The morphology of the composites varied with the dopant. Using scanning electron microscopy (SEM), the typical cauliflower structure was observed for the chloride-doped films, tubular-like structures were seen for the methyl orange-doped polymer films and the oxacillin-doped polymer films were smooth. The adhesion properties were tested using the “peel-test” and the adhesion properties improved with the addition of the chitosan layer. A constant potential was used to release methyl orange and oxacillin from the corresponding composites, and the stimulated release was investigated at various potentials, while the release was also investigated at open-circuit potentials. UV-visible spectroscopy was used to determine the concentrations of methyl orange and oxacillin. The release of methyl orange increased with an increase in the release period and as the applied potential was varied from 0.30 V to −0.60 V vs SCE. The release of oxacillin, on the other hand, did not vary significantly as a function of the applied potential, but did vary over time. The presence of chitosan did not significantly influence the release of oxacillin at 0.30 V vs SCE or at open-circuit potentials but did have an effect on the release at −0.60 V vs SCE.

    Item Type: Thesis (PhD)
    Keywords: Electrochemical synthesis; polypyrrole/chitosan films; molecular anions;
    Academic Unit: Faculty of Science and Engineering > Chemistry
    Item ID: 6034
    Depositing User: IR eTheses
    Date Deposited: 17 Apr 2015 09:09
    URI:

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