Conducting polymers electron-spin-resonance

The charged quasiparticles can be probed by electrical dc conductivity measurements (for polarons), magnetic susceptibility (for polarons and bipolarons), electron-spin resonance (ESR) (for polarons) and optical measurements (for polarons and bipolarons). As ESR is well suited for studying spin-carrying polarons, optical modification of the ESR (optically detected magnetic resonance ODMR) can be applied to link the emissive or absorbing properties of the polymer with its spin state. 

The direct synthesis by anodic oxidation of a new series of electrically conducting poljnners is described.. Our polymers derive from sulfur and/or nitrogen containing hetero-cycles such as 2-(2-thienyl)pyrrole, thiazole, indole, and phthalazine. The anodic oxidation of these monomers is carried out in acetonitrile solutions containing tetrabu-tylammonium salts (TBA X ) ith X = BF, tetraethylammonium salt, TEA H C-C H -S0. Characterization of the materials by electrical conductivity, electron spin resonance, uv-visible spectroscopy, and cyclic voltammetry is discussed. 

Methods of Characterization The polymers were characterized by four-probe electrical conductivity measurements between room temperature and liquid nitrogen, electron spin resonance (Varlan E-line series), scanning electron microscopy (Hitachi 520), cyclic voltammetry (Princeton Applied Research Instruments), and uv-vlsl-ble spectroscopy (Perkin Elmer 330). 

The electropolymerization of fluorene (Fig. 26) produces a polymer with a conductivity of 10 S cm. By functionalizing carbon 9 of the five-membered ring, substituted fluorenes have also been oxidized to form polymers of 9-methylfluorene, 9,9 -dimethylfluorene, and 9-phenylfluorene. These polymers gave comparable voltammograms, which seems to indicate that the substituents are not directly involved in the polymerizations. The doped polymers contained tetrafluoroborate anions, but their conductivities were very low [382,383]. The samples were analyzed by elemental analysis, infrared spectroscopy, electron spin resonance, and scanning electron microscopy. 

Within the past decades electron spin resonance (ESR) spectroscopy has become an indispensable technique in electrochemical research. It has proved its effectiveness in establishing many reaction mechanism in electro-organic synthesis. The latest development is the study of charge carrier generation in conducting polymers by simultaneous ESR spectroscopic and electrochemical measurements. The following electrochemical technique can be linked to in-situ ESR studies... 

Electron spin resonance (ESR) has an even longer standing history in the investigation of adsorption layers than NMR methods, due to the higher sensitivity. Its disadvantage is to require a spin probe, that can disturb the local molecular environment, which is a critical issue on molecular dimensions in monolayers. ESR and NMR methods can be considered complementary sources of information, and some of the very early NMR studies of grafted polymers at interfaces were in fact conducted complementarily to ESR [10]. A review of the application of ESR techniques to polymers at solid interfaces is given by Hommel [II]. 

Jing, F., Hou, M., Shi, W, Fu, J., Yu, H., Ming, P. and Yi, B. (2007) The effect of ambient contamination on PEMFC performance. J. Power Sources 166, 172-176 Kadirov, M. K., Bosnjakovic, A. and Schlick, S. (2005) Membrane-derived fluorinated radiceds detected by electron spin resonance in UV-irradiated Nafion and Dow ionomers Effect of counterions and H O - J- Phys. Chem. B 109, 7664-7670 Kelly, M. J., Egger, B., Fafilek, G., Besenhard, J. O., Kronberger, H. and Nauer, G. E. (2005a) Conductivity of polymer electrolyte membranes by impedance spectroscopy with microelectrodes. Solid State Ionics 176, 2111-2114... 

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