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Title: Gravimetric and optical studies of electroactive film dynamics
Author: French, Heidi Marie
Awarding Body: University of Leicester
Current Institution: University of Leicester
Date of Award: 2002
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The novel combined Electrochemical Quartz Crystal Microbalance-Probe Beam Deflection (EQCM-PBD) technique was used to study electroactive film dynamics and determine the individual contributions made by cation, anion and solvent species to the overall redox switching mechanism. The interpretation of the responses was extended to investigate the nature of the species transfer and film thickness changes in response to volume constraints. Studies of nickel hydroxide films in LiOH electrolyte show that hydroxide is the only detected ion transferring across the electrode/electrolyte interface to maintain electroneutrality. However, there is significant contribution made by protons, which are detected indirectly as H2O. The rigid nature of the film lattice constraints on the volume within the film and results, unusually in solvent transfer being forced into the same timescale as hydroxide ions. The mechanism for a- and b- phase redox switching differs only in the balance between hydroxide and proton (H2O) contributions to electroneutrality. The volume between layers in the film lattice defines this balance. The investigation of various polypyrrole and modified polypyrrole film systems exposed to a range of electrolytes highlights the effect of anion size on the predominant ion transfer maintaining film electroneutrality and the film volume changes accompanying this process in this non-rigid material. The variation in experimental timescale employed allowed further separation of the ion, salt and solvent transfers observed. The immobilisation of the polymeric polystyrenesulphonate (PSS) anion in the polypyrrole film matrix was shown to change the ion transfer properties of the film, which can be controlled as a function of electrolyte concentration. Salicylate anions were also used to create 'templated' PPy films, which indicated large solvent contributions. Surface roughness is shown to be a determining factor of the bulk properties of the 'templated' polymer film.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available