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|Title:||[M(salen)]-based conducting polymer films|
|Authors:||Tedim, Joao Andre da Costa|
|Presented at:||University of Leicester|
|Abstract:||This thesis reports the preparation and characterisation of poly[M(salen)] (M=Ni) conducting films bearing crown ether receptors, which were prepared via oxidative polymerisation of the [Ni(salen)] monomer. Electrochemical techniques showed that the resulting modified electrodes are electroactive, and that the electrochemical response is ligand-based. Moreover, this response was found to change irreversibly in the presence of metal cations (Cs +, Mg2+ and Ba2+), indicating the potential use of these films as sensing systems. The local structure around Ni atoms was studied by X-ray absorption spectroscopy, and found to remain unchanged regardless of the sample physical state, occurrence of polymerisation, and changes in the polymer doping state or ion uptake. For films bearing a small and 'rigid' pseudo-crown, data show that Ba uptake occurs by allocation of the cation within the pseudo-crown. However, for films bearing the large and flexible crown 2+ ether macrocycles, Ba is coordinated to a very low number of oxygen donor atoms, which is unexpected according to solution complexation concepts. This allows more Ba2+ to bind to the polymer at the cost of less selectivity towards analyte size. Acoustic wave sensor and microscopic techniques showed that the mechanical properties of films bearing crown ether macrocycles depends on the amount of deposited electroactive material. Thin films (r < 15 nmol cm" ) consist of a uniform layer of polymer with monodisperse, small polymer islands on the top, whereas thick films (r > 100 nmol cm" ) are rough, with an underlying uniform layer decorated with large heterogeneous islands of polymer. These large islands are mechanically quite different (more liquid-like) from the dense, inner layer. Finally, the incorporation of multi-walled carbon nanotubes in the poly Ni(sa/e) matrix enhances the electronic/electrochemical properties of the conducting polymer, opening a new route towards the optimisation of these systems.|
|Rights:||Copyright © the author. All rights reserved.|
|Appears in Collections:||Theses, Dept. of Chemistry|
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