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Title: Electronic properties of novel conducting polymers
Author: Haynes, D. M.
Awarding Body: University of Wales Swansea
Current Institution: Swansea University
Date of Award: 1997
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For some years a dynamic international research effort has focused on developing novel molecular materials which have interesting conducting and semiconducting properties. This thesis is concerned with the investigation of several novel organic polymers which fall into this category. The first part of the work concerns the DC characterisation of three conjugated polymers: poly[2,5-dibutoxy-1-(1'2'-ethynyl)-4-benzene] (A) poly[2,5-dibutoxy-1-(1'4'-buta-1',3'-diynyl)-4-benzene] (B) and poly-p-phenylene-vinylene (C). In their intrinsic state all these materials are quantitatively similar with band gaps of approximately 2.5 eV and room temperature conductivities of around 10-15 Ω-1cm-1. Upon doping with Ferric Chloride the conductivity of Material C is observed to rise dramatically, peaking at around 15 Ω-1cm-1. In contrast Materials A and B remain insulating on doping. The temperature dependence of the conductivity and thermopower of doped films of Material C suggests that the mechanism of charge transport changes at a critical temperature (Tc). This increased with increasing doping. Above Tc the transport mechanism is thought to be associated with hopping within a band of localised states which are intrinsic to the material. Below Tc it is likely that transport occurs within localised states associated with the presence of doping ions. The second part of the work concerns the study of the electrochromic materials poly[1,4-dithienylbenzene] (D) and poly[1,3-dithienylbenzene] (E). Both materials have been electrochemically polymerised and form coherent films which undergo reversible colour changes on application of a suitable potential. Display elements based on the materials have reached the 'proof of concept' stage. The displays have contrast ratios of around 6 and exhibit lifetimes greatly in excess of 1000 cycles. The degradation of the displays has in some instances been related to the quality of the film surface and this has been investigated using image analysis techniques.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available