Conducting polymers polypyrroles and

More recent studies have focussed on the characterization of the conductive polymer, polypyrrole, and its use as a coating for acoustic wave vapor sensors [74-77]. One advantage of polypyrrole is that it can be generated directly on an... 

The principle is to activate molecular oxygen, by the Mn porphyrin entrapped in the conductive polymer (polypyrrole), and thus to form oxo species at the electrode surface. Then, these oxo complexes can oxidize the hydrocarbons or phenol. The catalyst should be regenerated and this can be done by electroreduction at a constant potential (typically at — 0.5 V/SCE in acetonitrile). Moreover, the solution should contain an axial base (i.e. imidazole), and an activator (benzoic anhydride) [165,172]. 

Imprinted polymers exhibiting, at the same time, electrical conductivity facilitate their assembly with an electrochemical transducer in an integrated device. In this context, the preparation of composite particles consisting of an electrically conducting polymer (polypyrrole) and an acrylic MIP should be mentioned [42]. The polypyrrole that was grown into the preformed porous MIP did not alter its recognition properties. However, in this way MIP particles could be mechanically and electrically connected to a gold-covered silica substrate. 

This reverse electrochemical control of the gel composition and volume is the basis for the singular electrochemical properties and the concomitant applications of conducting polymers. Reactions and properties based on polypyrrole films can be summarized as shown in Table 5 and below ... 

The stoichiometry of the redox reactions of conducting polymers (n and m in reactions 1 and 2) is quite variable. Under the most widely used conditions, polypyrroles and polythiophenes can be reversibly oxidized to a level of one hole per ca. 3 monomer units (i.e., a degree of oxidation, n, of ca. 0.3).7 However, this limit is dictated by the stability of the oxidized film under the conditions employed (Section V). With particularly dry and unreactive solvents, degrees of oxidation of 0.5 can be reversibly attained,37 and for poly-(4,4 -dimethoxybithiophene), a value of n = 1 has been reported.38 Although much fewer data are available for n-doping, it appears to involve similar stoichiometries [i.e., m in Eq. (2) is typically ca. 0.3].34,39"41 Polyanilines can in principle be reversibly p-doped to one... 

Figure 4 compares cyclic voltammograms for a redox polymer (poly-[Fe(5-amino-1,10-phenanthroline)3]3+/2+)91 and p-doping and undoping of a conducting polymer (polypyrrole).92 The voltammogram for the redox... 

Figure 4. (A) Cyclic voltammograms over a range of scan rates for a redox polymer (poly-[Fe 5-amino-1,10-phenanthrotme)3]3+/>)91 and (B) p-doping and undoping of a conducting polymer (polypyrrole) (B). [(A) Reprinted from X. Ren and P. O. Pickup, Strong dependence of the election hopping rate in poly-tris(5-amino-1,10-phenan-throline)iron(HI/II) on the nature of the counter-anion J. Electroanal. Chem. 365, 289-292,1994, with kind permission from Elsevier Sciences S.A.]...

The final step entailed coating both the inner and outer surfaces of the LiMn204 tubules with the conductive polymer polypyrrole [125]. It has been shown that such LiMn204/polypyrrole composite electrodes have lower resistance and higher capacity than electrodes prepared from LiMn204 alone [125]. Furthermore, the high porosity and fast (relative to... 

Fig. 11.8. Current density as a function of rotation rate during growth of electrodeposited polypyrrole film at 0.550 ( ), 0.600 ( ), 0.650 (T), and 0.700 ( ) V. (Reprinted with permission from D. J. Fermin, M. Mostany, and B. Scharifker, Electronically Conducting Polymers Synthesis and Electrochemical Properties of Polypyrrole, Curr. Topics Electrochem. 2 132-136, 1993.)...

An optically active and electroconductive polymeric sorbent was prepared by coating the PS-L-proline-Cu(II) beads with conducting polymer polypyrrole. Applying a potential difference of 1.5 V to the column, racemic lysine and aspartic acid were separated according to their charge characteristics and were simultaneously resolved with respect to their optical isomerism. 

An interesting application is photosensitized polymerization of pyrrole (431) using [Ru(bpy)3]3 + to give a conducting polymer, polypyrrole (432), in aqueous solution or in a polymer matrix (Scheme 6.205).1236 The acting ground-state electron acceptor, [Ru(bpy)3]3 +, is obtained in the initial electron transfer step between an excited [Ru(bpy)3]2+ and [Co(NH3)5C1]2+ ion. 

This diol was mixed with other diols, then reacted with diisocyanates to form polyurethanes. The electrically conducting polymers, polyaniline and polypyrrole, prevent corrosion of steel.105 One of the best formulations uses polyaniline with zinc nitrate, which is then covered with an epoxy resin topcoat. Polyorganosiloxanes have been grafted to starch using the sol-gel method with alkoxysi-lanes. These materials have been complexed with cerium ions to provide corrosion protection for aircraft that is expected to be 50% cheaper than conventional coatings.106... 

Aizawa has studied an enzyme (metal) electrode based on immobilized GOD, which is a redox enzyme [66]. Interfacing in this type of biosensor requires facilitation of electron transfer from the active site of the enzyme protein to the metal electrode. Various methods have been used, such as electron mediators, electron promoters, and molecular wires, to accomplish this purpose. For example, a conducting polymer, polypyrrole, formed by electropolymerization on the electrode surface, was used to form electron wires which can facilitate electron transfers to and from the metal electrode. 

Figure 14-18. Covalent binding of enzymes to the conducting polymer polypyrrole. The reaction sequence shows the functionalization of the electrochemically deposited polymer film by nitration and subsequent electrochemical reduction.

A. Ramanaviciene, W. Schuhmann, and R. Ramanavicius, AFM study of conducting polymer polypyrrole nanoparticles formed by redox enzyme - glucose oxidase - initiated polymerisation, Colloid Surf. B., 48(2), 159-166 (2006). 

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