Doped conductive polymers charge transfer reactions

In many cases the important property will actually be the permeability, which is the product of the diffusion coefficient and the solubility of the dopant in the polymer. The solubility is determined by the degree of interaction between the diffusant and the polymer. The picture is further complicated, since reactions may take place so that several different species are diffusing. The reaction of a gaseous dopant with a conducting polymer is a complicated diffusion and reaction process. We must consider the solubility and diffusion of the molecular gas, the charge-transfer reaction to dope the polymer, the diffusion of the resulting ions in the doped (intercalated) structure and any reaction between the dopant ions and the polymer which may lead to covalent bonding. 

Self-doping has also been studied with poly(3-alkylsulfonate-thiophenes) [7-9]. The self-doped polythiophenes have a SO3H group at the end of the alkyl side chain. However, in order to obtain good conductivities, the charge transfer reaction has to be driven electrochemically to remove the cation (H+ or Na+) of the sulfonic acid out of the polymer. Otherwise this kind of self-doped polythiophenes have a very low conductivity in the dried state due to the protonation of the thiophene rings [75]. 

The adhesion power of metal electrode to perfluorosulphonic polymer is used to modify the surface of a single electrode for the analysis of electrochemical reactions of special interest. Nafion -coated electrodes have been developed by Rubinstein Bard" . Various electron-conducting materials (glassy carbon, gold, platinum) are used as support for the Teflon layer. With these coated electrodes, the mechanisms of mass and charge transfer in the perfluorosulphonic material have been investigated and also the catalytic and photochemical properties of polymer doped with various chemical species . ... 

These reaction formulae indicate that the electron transfer taking place at the metal I polymer interface is accompanied by ionic charge transfer at the polymer Isolation interface, in order to maintain the electroneutrality within the polymer phase. Counterions usually enter the polymer phase, as shown above. However, less frequently the electroneutrality is established by the movement of co-ions present in the polymer phase, e.g., in so-called self-doped polymers. Oxidation reactions are often accompanied by deprotonation reactions, and H+ ions leave the film, removing the excess positive charge from the surface layer. It should also be mentioned that simultaneous electron and ion transfer is also typical of electrochemical insertion reactions however, this case is somewhat different since the ions do not have lattice places in the conducting polymers, and both cations and anions may be present in the polymer phase without any electrode reaction occurring. The es-... 

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