A new β and <I>N</I>-substituted pyrrole, <I>N</I>-trimethylsilylethoxymethyl-3-methyl-4-pyrrole carboxylate ethyl ester (MPCE-SEM) is synthesised and copolymerised electrochemically with unsubstituted pyrrole to gives free-standing films for conductivity measurements. The electrochemical polymerisation of MPCE-SEM gives only soluble dimers and oligomers rather than polymers because the steric constraints stabilise the oligomeric cation radical of MPCE-SEM. The thiophene monomers containing mesogenic group at the 3-position via an alkyl chain are synthesised and polymerised chemically to give insoluble, infusible polymers and do not exhibit liquid crystalline behaviour. The conductivities of pressed-pellets of the polymer powders are lower than 10<SUP>-5</SUP>S/cm. The electrochemical polymerisation of the thiophene monomers containing mesogenic group of 4-methoxyazbenzen-4'-yloxy or 4-butylazobenzen-4'-yloxy in dichloromethane solution gives a low yield of polymers, which is accompanied by the formation of soluble dimers and oligomers as well as degradation of the resulting polymer and the mesogenic group. Poly{<I>N </I>-11-[(4-cyanobiphenyl-4'-yloxy) undecyl] pyrrole} obtained from chemical polymerisation of the corresponding monomer shows high molecule weight, is soluble in common solvents and fusible showing smectic A liquid crystalline behaviour. This polymer in the melt (175<SUP>o</SUP>C) has a conductivity of 6.6 x 10<SUP>-15 </SUP>S/cm. X-ray photoelectron spectrometry analysis on the melt processed film gives an estimated doping level of an anion every 6-7 monomer units. Electrochemical oxidation of the <I>N</I>-substituted pyrrole monomers gives the electroactive conjugated free-standing polymer films. The conductivities of the free standing polymer films are lower than 10<SUP>-4</SUP> S/cm. A conducting copolymer containing a side chain liquid crystalline group, poly{<I>N</I>-8-[(4-cyanobiphenyl-4'-yloxy)octyl]-2,5-di(2-thienyl) pyrrole} can be obtained electrochemically from the corresponding monomer. The polymer is slightly soluble in chloroform giving a dark green solution but is not liquid crystalline.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:312356 |
| Date | January 2000 |
| Creators | Chen, Yu |
| Publisher | University of Aberdeen |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
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