Electrochemical studies of conducting polymers

Loganathan, Kavithaa (2005) Electrochemical studies of conducting polymers. Doctoral (PhD) thesis, Memorial University of Newfoundland.

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Abstract

This project addresses the development of low band gap organic materials with high intrinsic conductivity which remains a big challenge for many conducting polymer based applications. New bridged bithiophene and fluorene systems were investigated. Results proved that the linkage of two bridged bithiophene moieties by a double bond, and bridging fluorene moieties by sulphur atoms can produce low band gap materials with low-lying LUMO energy levels. This new approach to the design of low band gap materials compliments the strategy of introducing electron withdrawing groups at an sp² carbon bridging a bithienyl precursor for producing n-type conjugated low band gap systems. Advanced polymerization techniques such as copolymerization (polymerization from solution of two monomers), homopolymerization of a comonomer (a molecule containing both monomer units) and working electrode rotation during polymer growth were developed to tune band gaps and enhance intrinsic conductivities. Investigations of copolymers with conjugated bridged bithiophene and fluorene systems support the donor acceptor strategy for band gap reduction. Hence, by advanced synthetic strategies, the band gap of a polythiophene derivative was tuned from 1.0 e V to 0.1 e V and its intrinsic conductivity was improved by an order of magnitude. Further, a variety of polyfluorene derivatives with band gaps ranging from 1.2 eV to 0.8 eV were synthesized and structureconductivity relationships were studied. These materials may have potential uses in electrochromic displays and related applications.

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