A study of the electrochemical oxidation and reduction of polyaniline
A study of the electrochemical oxidation and reduction of polyaniline
The mechanisms of the reactions involved during oxidation and the reduction of polyaniline films were investigated under time-resolved conditions using a Pt ultramicroelectrode. Potentiostatic and potentiodynamic methods were used for the study of the redox processes at different pH values but constant ionic strength and also at low temperature.
The redox behaviour of polyaniline changes as the pH is increased in the same way as observed when the temperature is decreased. The rates of the redox processes at low pH values are extremely fast and are largely controlled by the rapid exchange of protons between the electrolyte and the polyaniline film. At high pH values the process is slower and is controlled by the slow ingress of anions.
The current response for oxidation at low pH values shows excellent agreement with the two-dimensional progressive nucleation model used to describe the formation of anodic films such as Hg2Cl2. This shows that during oxidation conducting strands propagate preferentially normal to the electrode surface followed by sideways expansion.
Choronopotentiometric studies coupled with reflectance measurements on polyaniline indicate rapid structural transformation from leucoemeraldine to emeraldine. The hysteresis noted in the reflectance shows that the structural changes depend on the direction of change, i.e. oxidation or reduction. The oxidation of leucoemeraldine proceeds by the formation of radical cations then dications.
The `memory effect' is shown to be related to incomplete reduction and slow structural transformations.
University of Southampton
1993
Vuki, Maika
(1993)
A study of the electrochemical oxidation and reduction of polyaniline.
University of Southampton, Doctoral Thesis.
Record type:
Thesis
(Doctoral)
Abstract
The mechanisms of the reactions involved during oxidation and the reduction of polyaniline films were investigated under time-resolved conditions using a Pt ultramicroelectrode. Potentiostatic and potentiodynamic methods were used for the study of the redox processes at different pH values but constant ionic strength and also at low temperature.
The redox behaviour of polyaniline changes as the pH is increased in the same way as observed when the temperature is decreased. The rates of the redox processes at low pH values are extremely fast and are largely controlled by the rapid exchange of protons between the electrolyte and the polyaniline film. At high pH values the process is slower and is controlled by the slow ingress of anions.
The current response for oxidation at low pH values shows excellent agreement with the two-dimensional progressive nucleation model used to describe the formation of anodic films such as Hg2Cl2. This shows that during oxidation conducting strands propagate preferentially normal to the electrode surface followed by sideways expansion.
Choronopotentiometric studies coupled with reflectance measurements on polyaniline indicate rapid structural transformation from leucoemeraldine to emeraldine. The hysteresis noted in the reflectance shows that the structural changes depend on the direction of change, i.e. oxidation or reduction. The oxidation of leucoemeraldine proceeds by the formation of radical cations then dications.
The `memory effect' is shown to be related to incomplete reduction and slow structural transformations.
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Published date: 1993
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Local EPrints ID: 462439
URI: http://eprints.soton.ac.uk/id/eprint/462439
PURE UUID: b0429b21-eabf-4f29-b8c7-68d2e0da19ff
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Date deposited: 04 Jul 2022 19:08
Last modified: 04 Jul 2022 19:08
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Author:
Maika Vuki
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