Strategies towards functionalised conducting organic copolymers
This thesis is concerned with the synthesis, characterisation and electropolymerisation of two species of functionalised heterocyclic compounds: a) thiophene and pyrrole monomeric systems b) thiophene, pyrrole and furan mixed trimeric systems. There are many motivations for introducing group substituents to conducting polymer systems e.g. plastic electronics such as new types of "smart" field effect transistors (FET) or modulation of LED emission frequency and sensors such as bio- or enzyme crown ether ion -sensors or even DNA detectors. The consequences of this usually result in poor electrical conductivity and/or physical properties of the materials. In this work we have sought to find routes to functionalised conducting polymer materials with good physical and electrical properties using two strategies (approaches): a) copolymerisation of functionalised monomers with unsubstituted compounds b) polymerisation of monosubstituted trimeric systems As a consequence thiophene and pyrrole monomeric systems were substituted with carbonyl and nitrile groups and characterised by cyclic voltammetry. These functionalised monomeric compounds underwent electrochemical homo- and/or copolymerisation. The resultant polymer films were analysed by absorbance/reflectance FT-IR and X-ray photoelectron spectroscopies. We have focused particularly on trimeric systems constructed from pyrrole, thiophene and furan units in which only the central ring bears functionality. Importantly our approach to the synthesis of these systems is based on a generic route involving ring closure reactions of substituted 1,4 diketones. Novel "2.5-Di(2-thienyl)" based trimeric systems, substituted at the β-position of the central ring, were synthesised. Electrochemical homopolymerisation of these single functionalised trimeric compounds gave fixed ratio copolymers, which are expected to exhibit high electrical conductivity. Particular interest was devoted to the electropolymerised poly-2, 5-Di-(2-thienyl)-3-pyrrole-valeric acid to investigate the bioelectrochemical interaction with the redox enzyme cyctochrome c. In every case useful data was provided, by analysing both, homo- and copolymer films, using a combination of spectroscopic techniques, including absorbance/reflectance FT-IR or X-ray photoelectron spectroscopy.