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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
1

Towards anisotropy in ordered conducting polymers

Chen, Yu January 2000 (has links)
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.

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