Redox polymers chemical

Figure 2.5 Schematic representation of the Au/MPS/PAH-Os/solution interface modeled in Refs. [118-120] using the molecular theory for modified polyelectrolyte electrodes described in Section 2.5. The red arrows indicate the chemical equilibria considered by the theory. The redox polymer, PAH-Os (see Figure 2.4), is divided into the poly(allyl-amine) backbone (depicted as blue and light blue solid lines) and the pyridine-bipyridine osmium complexes. Each osmium complex is in redox equilibrium with the gold substrate and, dependingon its potential, can be in an oxidized Os(lll) (red spheres) or in a reduced Os(ll) (blue sphere) state. The allyl-amine units can be in a positively charged protonated state (plus signs on the polymer...

Josh Gallaway was born in Waverly, TN, in 1974 and lived there until attending Case Western Reserve University in 1992, where he earned a B.S. in chemical engineering. Since 2002, he has been a graduate student at Columbia University, studying redox polymer-enzyme systems for use in biofuel cells. 

Chemical Reviews, 2004, Vol. 104, No. 10 Table 3. Redox Polymer Anode Mediators... 

If the surface of a metal or carbon electrode is covered with a layer of some functional material, the electrode often shows characteristics that are completely different from those of the bare electrode. Electrodes of this sort are generally called modified electrodes [9] and various types have been developed. Some have a mono-molecular layer that is prepared by chemical bonding (chemical modification). Some have a polymer coat that is prepared either by dipping the bare electrode in a solution of the polymer, by evaporating the solvent (ethanol, acetone, etc.) of the polymer solution placed on the electrode surface, or by electrolytic polymerization of the monomer in solution. The polymers of the polymer-modified electrodes are either conducting polymers, redox polymers, or ion-exchange polymers, and can perform various functions. The applications of modified electrodes are really limit-... 

In the same study, redox polymers (223) were prepared that contained pendant viologens (Scheme 108). An active reducing agent was obtained by chemical reduction with dithionite or zinc, electrochemically, or by exposure to light. Utilization of the reduced poly(viologen) (224) as an electron transfer mediator was demonstrated by addition of a catalytic amount of the polymer to a mixture of zinc powder, ethyl benzoylformate (225) and water-acetonitrile (1 5). A quantitative yield of ethyl mandelate (226) was obtained after two days at room temperature (Scheme 109). Without the polymer, no reaction was observed after a month. 

An enormous number of polymers have been used to prepare chemically modified electrodes. Some examples are given in Table 13.2 Albery and Hillman provide a more extensive list [8]. As indicated in Table 13.2, these polymers can be divided into three general categories—redox polymers, ion-exchange and coordination polymers, and electronically conductive polymers. Redox polymers are polymers that contain electroactive functionalities either within the main polymer chain or in side groups pendant to this chain. The quintessential example is poly(vinylferrocene) (Table 13.2). The ferrocene groups attached to the polymer chain are the electroactive functionality. If fer-... 

Chemically modified electrodes (CMEs) for electrocatalytic oxidation of the reduced form of the nicotinamide adenine dinucleotide cofactor (NADH) are discussed. The work of the authors in the field is reviewed. CMEs based on adsorbed polyaromatic redox mediators (phenoxazines and phenothiazines) and the deposition of aqueous insoluble redox polymers are described. 

Polymer film electrodes are prepared either by evaporation technique or by -> electropolymerization. Redox polymers that are usually synthesized chemically are dissolved in a suitable solvent, placed as a droplet on the surface of a metal (or dip-coating, spin-coating techniques are applied) and the solvent is subsequently left to evaporate. The electrode can be used in other solvents in which the polymer is insoluble. Conducting polymer layers are usually developed by electropolymerization directly on the surface of the metal. 

Electrical communication between redox centers of glucose oxidase and electrodes via electrostatically and covalently bound redox polymers. Journal of the American Chemical Society, 111, 2357-2358. 

Andrieux, C.P, Haas, O., and Saveant, J.-M. 1986. Catalysis of electrochemical reactions at redox polymer coated electrodes. Mediation of the Fe(III)/Fe(ll) oxido-reduction by a polyvinylpyridine polymer containing coordinatively attached bisbipyridine chlororuthenium redox centers. Journal of the American Chemical Society 108, 8175-8182. 

These are presented by two subclasses of electroactive polymer (i) -conjugated polymers of both organic and inorganic nature [5-15] and (ii) conventional redox polymers [26], and by inorganic ion-insertion (intercalation) compounds [27, 28[ (see the top of Scheme 11.1b). Despite the different nature of their chemical bonds, all of these compounds are mixed, electronic-ionic conductors [29], and hence, their electronic and/or ionic conductivity is expected to change with the applied potential in a predictable, characteristic manner (see Section cl 1.4). 

One of the interesting things about the redox polymers is their use in the creation of the molecular electronic devices.3-5 Redox polymer films on electrodes have been fabricated using chemical modification, electrochemical polymerization, polymer coating, and so on.88 Recently, stepwise complexation methods have been employed to fabricate multiple complex layers.89,90,91 In this section, the stepwise preparation of bis(tpy)metal polymer chains by combining terpyridine (tpy) ligand self-assembled monolayer (SAM) formation and metal-tpy coordination reactions is described as an example. This method realized the formation of a desired number of polymer units and a desired sequence of Co-Fe heterometal structures in the polymer chain.92... 

The metallocyanates are a large class of compounds, the most widely studied of which are probably Prussian Blue (Na[FeFe(CN)fi]) in its various oxidation states and nickel hexacyanoferrate (Na2[NiFe(CN)6]). These materials can be prepared chemically or electrochemically as thin films on surfaces [200]. They differ from redox polymers in that, because of their lattice structure, there is significant interaction between the redox sites within the film and there is strong size-charge selectivity towards incorporated counter-ions. This arises because the counter-ions have to be accommodated within the lattice structure and this... 

The interest in these polymers has been accelerated by their applicability in the area of chemically modified electrodes (Abruna 1988 Kaneko and Wohrle 1988). Especially biosensor applications are very interesting applications for redox polymers... 

Electroactive polymers have a number of attractive features that account for this continuing interest. First they present a distributed array of catalytic sites. Thus in contrast to monolayer chemically modified electrodes, there are potentially a much greater number of reactive sites that can contribute to the catalytic current. Since these sites are distributed throughout the film, it is essential to consider the mass transport of reagents into the film and the mass transport of products out of these films when studying the overall kinetics of these processes. The coupled mass transport and kinetics in redox polymer films have been investigated in some detail, and good models exist for these processes. ... 

Conventional redox polymers can also form the basis of electrochemical transistors. Conventional redox polymers have lower maximum conductivity/ and yield devices having lower values of Ijy than conducting polymers or metal oxides. Conventional redox polymers offer an important design advantage, however. Nearly any stable redox active material can be incorporated into a polymeric system to form a conventional redox polymer. This allows the fabrication of devices with a wide range of chemical sensitivities. 

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