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Title: Synthesis and properties of highly regular electroactive polyaromatics
Author: Jenkins, I. H.
Awarding Body: University College of Swansea
Current Institution: Swansea University
Date of Award: 1991
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The work described involves the synthesis and doping of conducting polymers containing both phenylene and thienylene units, linked in a highly regular and defined fashion. Chapter one begins with a review of the present strategies and the criteria involved in the synthesis of certain well known conjugated polymers such as polyacetylene (PA) and poly-(p-phenylene) [PPP]. PPP, as well as heteroaromatic polymers, such as polythiophene (PT) and polypyrrole are synthsised by both chemical and electrochemical means, the latter giving rise to mechanically tough and durable films. This is followed by a look at the morphology and structure of chemically produced polymers PPP and PA as well as the electrochemically formed polymer PPy and PT. The last section in chapter one gives a brief insight of the many potential applications of conducting polymers, especially in the realms of battery electrodes, the protection of photoanodes and electrochromic display devices. Chapter two begins with an assessment of the problem of structural anomalies in electrochemically grown conducting polymers. The present methods and one very recent method of obtaining thienylene-phenylene co-polymers are discussed, followed by a review of transition metal catalysed cross-coupling reactions and their high applicability in the synthesis of highly defined polymeric materials. Previous work at Swansea on the preparation of phenylene-furylene polymers and thiophene-phenylene oligomers is given. The mechanisms of cross-coupling are briefly discussed. Electropolymerisation (anodic oxidation) of small preformed oligomers such as 1,3-bis(2'-thienyl)benzene and 4,4-bis(2'-thienyl)biphenyl give polymer films with good electrochromic properties. Chapters three and four describe the author's own contribution towards highly regular thienylene-phenylene co-polymers. Poly(1,4-phenylene 2'-5'-thineylene) was synthesised in excellent yield by the coupling of 1,4-bis(2'-thineyl)benzene, which had been metallised at the 5'-5-positions with zinc chloride, with 1,4-dibromobenzene in the presence of a transition metal catalyst. This polymer however was extremely insoluble and efforts were later made to render similar polymers soluble by incorporating various substituent groups at the 2,5-positions of the phenylene moiety. Using 1,3-dibromobenzene in this reaction it was shown how the linkages could be altered without loss of the high structural integrity of the polymer. Similarly, 4,4-dibromobiphenyl was utilised, and showed how the stoichiometry of the polymer backbone could be altered by a highly regular and defined incorporation of biphenyl units. The synthetic work was concluded with an assay of the effect of different metal groups on the chain length of the polymer, molecular weights being estimated by gel permeation chromatography. Finally, chapter five concludes with the doping and subsequent improvement of electrical conductivity of the polymers synthesised by the author.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available