Polyvinylferrocene redox

The application of two successive redox polymer layers at an electrode surface gives rise to rectifying properties because the electron transport between the electrode and the outer layer has to be mediated by the inner redox polymer Among several conbeivable situations, the one where the inner layer possesses two reversible redox potentials (e.g. a Ru"(bipy)j polymer) and the outer layer has one redox transition with a potential between the former ones (e.g. polyvinylferrocene) is most interesting gjj electrode device has two opposite-sign rectifying... 

By setting the ratio of the oxidized and reduced forms of a redox couple in an electrode coating film to unity, the potential of this electrode in an inert electrolyte is poised at the half-wave potential of the couple. This has indeed been shown for platinum wires coated with polyvinylferrocene or ferrocene modified polypyrrole But the long term stability of these electrodes during cell connection... 

The redox active polymer films might bear the mediator group attached either covalently to the polymer backbone (polyvinylferrocene, Ru(II) complexes of polyvinylpyridine, etc.) or electrostatically within the ion-exchange polymer (e.g. in Nation, cf. Section 2.6). 

Similar words of caution belong with redox polymers. Polyvinylferrocene typifies the type of polymeric compound where the redox centre is an integral part of the polymer. In view of ferrocene s well tried mediation talents this would seem an ideal choice of model, but the heterogeneous charge transfer rate constant for this redox polymer is typically 102 - 103 lower than the solution species (47) and although catalytic activity can usually be partially retained the kinetics of electron transfer are undesirably slow.. 

Earlandite structure, 849 Electrical conductivity metal complexes, 133 tetracyanoplatinates anion-deficient salts, 136 Electrical properties metal complexes, 133-154 Electrocatalysis, 28 Electrochemical cells, 1 Electrochemistry, 1-33 hydrogen or oxygen production from water coordination complex catalysts, 532 mineral processing, 831 reduction, 831 Electrodeposi (ion of metals, 1-15 mineral processing difficulty, 831 Electrodes clay modified, 23 ferrocene modified, 20 nation coated, 15 polymers on, 16 polyvinylferrocene coated, 19 poly(4-vinylpyridine) coated, 17 redox centres, 17 Prussian blue modified, 21 surface modified, 15-31 Electrolysis... 

Poly(8-quinolinol) electrode coatings, 19 Polysaccharides metal complexes geochemistry, 868 Polyselenides metal complexes geochemistry, 854 Polytyramines electrode modification, 23 Polyvinylferrocene electrode coatings, 19 attachment, 19 Poly(N-vinylimidazole) metal complexes color photography, 109 Poly(4-vinylpyridine) electrode coatings, 17 redox centres, 17 electrodes, 16 Porins... 

The oxidation or doping process of electroactive polymers involves the simultaneous insertion of charge and a counterion to balance the charge. For redox polymers such as polyvinylferrocene the process may be written... 

Polyvinylferrocene has also been shown to have nearly ideal stoichiometric behaviour by quartz crystal microbalance gravimetry. It will be demonstrated that only anions are inserted and removed during the redox process up to the cyclic voltammetry peak region, and that the mass changes associated with this process are confirmed by QCM measurements. Concurrent cyclic voltammetry and QCM measurements permitted the calculation of the mass change to be expected from the quantity of charge passed, and this was compared with the observed mass change (QCM). In LiClO solutions in acetonitrile, only the anion was involved in the redox process up to the peak. 

Since suitable conducting polymers with anionic backbones are not available, we have resorted to a more complex approach for cation binding. Following Martin s workio on terpolymer redox films of polyvinylferrocene, we produced a new type of composite polymer, of cationic poly-(N-methylpyrrole) (PMP" ) with anionic poly-styrenesulfonate (PSS ). Upon reduction of a film of this material, cations are taken up. Thus, the entangled polymeric anion is not flushed out by reduction of the pyrrole units. Instead, cations are incorporated to balance the sulfonate charges. This has been shown for a variety of cations including protonated dopamine. The scheme below shows how this polymer works to bind protonated dimethyldopamine (DH ) cathodically and to release it anodically. 

Fig. 29) Two adjacent microelectrodes were derivatized by stepwise electrochemical polymerization. First a polymer viologen film (BPQ )n (related to 4) on one electrode and then a polyvinylferrocene (PVFc) film (related to 11) on the other electrode were obtaineo from the corresponding monomers by reductive and oxidative depositions, respectively. Small spacing between the two microelectrodes is crucial because for these materials the maximum conductivity is much lower than that of polymers such as 14,17, and 20 The redox levels are as follows E (BPQ +/+) = —0.55 V, E°(PVFc /°) = 0.4 V vs SCE. The redox reaction at the interface immersed in an aqueous electrolyte containing LiCIO occurs at a good rate only in one direction because the reaction in Eq. (20) is thermodynamically downhill. 

The mainstream application of PBD techniques has been the study of redox coupled ion exchange of electroactive films [9]. The electroactive material could be redox polymers (e.g., polyvinylferrocene [10]), conductive polymers... 

Mao X, Rutledge GC, Hatton TA. Polyvinylferrocene for noncovalent dispersion and redox- controlled precipitation of carbon nanotubes in nonaqueous media. Langmuir 2013 29 9626-34. 

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