Modified polypyrrole

Sodium dodecyl sulfate has been used to modify polypyrrole film electrodes. Electrodes synthesized in the presence of sodium dodecyl sulfate have improved redox processes which are faster and more reversible than those prepared without this surfactant. The electrochemical behavior of these electrodes was investigated by cyclic voltametry and frequence response analysis. The electrodes used in lithium/organic electrolyte batteries show improved performance [195]. 

Table 1. N-substituted pyrroles employed in the preparation of redox-Modified polypyrrole films on electrodes...

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... 

Further interesting redox modified polypyrrole films were prepared e.g. a polymeric copper phenanthroline complex that can be reversibly de- and re-metallated because it retains the pseudotetrahedral environment after decomple-xation, A very diversified electrochemistry is displayed by polypyrrole films containing electron donor as well as electron acceptor redox centers in the same film... 

The catalytic activity of viologen modified polypyrrole electrodes in preparative elK tror luctions has been extended from vicinal to geminal poly-... 

More recently Bouzek et al. investigated the effect of the preparation conditions of Pt-modified polypyrrole films on their electrocatalytic properties for the HOR [26]. Three methods were considered (1) cathodic deposition of Pt from H2PtCl6 in the previously synthesized film, (2) incorporation of colloidal Pt particles during the electropolymerization of polypyrrole (3) incorporation of [PtCU] as a counter-ion during the electropolymerization process and its subsequent reduction. Only the first two methods lead to active electrocatalytic films, whereas the last one gives very poor catalysts, maybe because the Pt particles are embedded in the PPy structure and therefore are not accessible to the reactant. 

Reiter, S., Habermtiller, K., and Schuhmann, W. (2001) A reagentless glucose biosensor based on glucose oxidase entrapped into osmium-complex modified polypyrrole films. Sensors and Actuators B, 79 (2-3), 150-156. 

Carbon dioxide electroreduction can be carried out on modified polypyrrole electrodes [81,82,180]. The active electrodes are obtained by electropolymerizalion of Re(L)(CO)3Cl complex, where L is a pyrrole-substituted ligand of various length. The active species is the immobilized rhenium complex. The main reaction product in acetonitrile is carbon monoxide, and preparative-scale electrolysis gave efficiencies as high as 90%. 

Biswas and Roy [118,119] studied the degradation and stability of chemically prepared polypyrrole substituted by phthalic anhydride (PPY-PhAn) and pyromellitic dianhydride (PPY-PMDA) by using a thermal analyser and IR spectroscopy. They found that the chemical modification enhanced the thermal stability of the modified polypyrrole as compared with... 

K. Bouzek, K.M. Mangold, and K. Jiittner, Platinum distribution and electrocatalytic properties of modified polypyrrole films, Electrochim. Acta, 46, 661-670 (2000). 

Y.C. Liu and B.J. Hwang, Mechanism of conductivity decay of polypyrrole exposed to water and enhancement of conductivity stability of copper(I)-modified polypyrrole, J. Electroanal. Chem., 501, 100-106 (2001). 

V.M. Jovanovic, S. Terzic, and A. Dekanski, Characterization and electrocatalytic application of silver modified polypyrrole electrodes, J. Serb. Chem. Soc., 70, 41-49 (2005). 

HabermuUer, K., A. Ramanavicius, V. Laurinavicius, and W. Schuhmaim. 2000. An oxygen-insensitive reagentless glucose biosensor based on osmium-complex modified polypyrrole. Electroanalysis 12 (17) 1383. 

In the last decade, Mn(III) porphyrin-modified polypyrrole films were reported and used to mimic electrochemically and advantageously the functioning of cytochrome P450, an enzyme of the monooxygenase type " . Indeed, various families of compounds, namely Mn(III) porphyrin derivatives such as 8,9,10,12... 

The synthesis of a modified polypyrrole requires that the modification introduced remains compatible with normal synthesis and with conservation of the semiconducting or conducting properties of the material. In pyrrole there are two positions which can be substituted in order to obtain conducting polymers the 3 (or ) ) position and the N position. 

Figure 14 Synthesis of oligonucleotide-modified polypyrrole. (Adapted from H. Korri-Youssoufi, F. Gamier, P. Srivastava, P. Godillot, and A. Yassar. J. Am. Chem. Soc. 119 7388-7389,1997. With permission.)...

Bouzek K, Mangold K-M, Juttner K. Electrocatalytic activity of platinum modified polypyrrole films for the methanol oxidation reaction. J Appl Electrochem... 

Loss of electroactivity, mechanical strength, and formation of carbonyl groups along with the formation of carbon dioxide were observed [175-181] when polypyrrole anode was cycled between charging and discharging in different electrolytic systems. However, in modified polypyrroles, the type of substituents at N, substituents on the pyrrole ring, and the conditions of synthesis also play an important role in deciding the stability of materials in electrochemical systems [175,182-185]. 

The thermal stability of chemically modified polypyrroles was studied by using a thermal analyzer and IR spectroscopy, and it was reported that the stability was enhanced in the order polypyrrole < polypyrrole-phthalic anhydride < polypyrrole- yromellitic... 

Foulds N.C. and Lowe C.R. (1988) Immobilization of glucose oxidase in ferrocene-modified polypyrrole polymers. Anal. Chem., 60, 2473-2478. 

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