| The goal of the first project was to explore the electrochemical and optical properties of substituted selenophenes and to compare them, where possible, to those of thiophene analogs. This fundamental work significantly contributed to the complete characterization of the first highly conductive polyselenophene, poly(3,4-ethylenedioxyselenophene) PEDOS 1, by the Bendikov group in 2008, which established the new field of conductive polyselenophenes. The research demonstrated that both the monomers and polymers of selenophene have lower oxidation potentials, lower band gaps, and are more planar than the corresponding thiophenes.;In order to explore the chalcogen backbone effect further, a di-methoxy tellurophene was synthesized and compared to di-methoxy thiophene and selenophene. This work resulted in the first synthesis of any polytellurophene, with synthate identity determined by in-situ electrospectroscopy.;Spectroelectrochemical and electrochemical experiments were conducted on fused molecules based on poly(thieno[3,4-b]thiophene in which one or both atoms were replaced with selenium. The results showed that the difference in aromaticity between thiophene and selenophene leads to a decrease in the band gap when selenophene is present in the backbone and an increase in band gap when selenium forms part of the peripheral ring fused to the backbone. Cyclic voltammetry on the polymer, combined with theoretical calculations, revealed the new materials poly(seleno[3,4-b]thiophene) and poly(seleno[3,4-b]selenophene) to be stable and suitable for both p and n-type doping.;Finally, 3,4-dibromo-thiophene and --selenophene were coupled in a novel Ni(COD)2 catalyzed process to yield [6]radialene and [8]radialene. The oxidation potentials of the selenium compounds were found to be about 0.12 V lower than those of the corresponding sulfur compounds, probably due to the polarizability of selenium atoms.;The goal of the second project was to find a conjugated conducting polymer to replace PPy or to improve the stability, and hence the lifetime, of nitrate ion-selective-electrodes (ISE) based on polypyrrole (PPy) by incorporating poly(3,4-ethylenedioxythiophene) (PEDOT) as a coating or in the formation of a copolymer. Excellent ISEs were obtained by copolymerizing pyrrole with EDOT or bis-EDOT in nitrate salt dissolved in either water or acetonitrile, respectively. These sensors demonstrated significantly increased stability and sensitivity in comparison to the parent polypyrrole-based ISE and other ISEs based on conjugated conductive polymers that were manufactured in the lab. A successful attempt to use a coated wire PVC membrane as the active layer showed the simplicity of such a construction. Morphological differences between the various sensor architectures and the success of the copolymer suggest a synergetic effect between the stability of PEDOT and the sensitivity of PPy. |
