Polypyrrole synthesis

Synthesis, properties, and applications of polypyrrole as a conducting polymer 97UK489. 

At this point it might be appropriate to comment on the conflicting requirements of the synthesis. The large interest which other conjugated polymers such as polypyrrole, polyanilinc or poly(parattracted originates, firstly, from their attractive physical properties, but also from the sim-... 

Here we introduce a personal point of view about the interactions between conducting polymers and electrochemistry their synthesis, electrochemical properties, and electrochemical applications. Conducting polymers are new materials that were developed in the late 1970s as intrinsically electronic conductors at the molecular level. Ideal monodimensional chains of poly acetylene, polypyrrole, polythiophene, etc. can be seen in Fig. 1. One of the most fascinating aspects of these polymeric... 

In 1979, Diaz et al. produced the first flexible, stable polypyrrole (PPy) film with high conductivity (1(X) Scm ). The substance was polymerized on a Pt-electrode by anodic oxidation in acetonitrile. The then known chemical methods of synthesis " usually produced low conductivity powders from the monomers. By contrast, electropolymerization in organic solvents formed smooth and manageable films of good conductivity. Thus, this technique soon gained general currency, stimulating further electropolymerization experiments with other monomers. In 1982, Tourillon... 

Besides synthesis, current basic research on conducting polymers is concentrated on structural analysis. Structural parameters — e.g. regularity and homogeneity of chain structures, but also chain length — play an important role in our understanding of the properties of such materials. Research on electropolymerized polymers has concentrated on polypyrrole and polythiophene in particular and, more recently, on polyaniline as well, while of the chemically produced materials polyacetylene stih attracts greatest interest. Spectroscopic methods have proved particularly suitable for characterizing structural properties These comprise surface techniques such as XPS, AES or ATR, on the one hand, and the usual methods of structural analysis, such as NMR, ESR and X-ray diffraction techniques, on the other hand. 

Figure 11 The reaction scheme for the polypyrrole precursor (11) synthesis (left top) with reagents and conditions (left hottom). Representative pyrrole (12) and thiophene (13 and 14)-based redox-active polypyrroles. (Adapted from refs. 32 and 33.)...

The synthesis of the first covalently attached carborane-containing polypyrrole was reported by Fabre and co-workers.141 The initial step involved the production of... 

X. Zhang, J. Zhang, R. Wang, T. Zhu, and Z. Liu, Surfactant-directed polypyrrole/CNT nanocables synthesis, characterization, and enhanced electrical properties. ChemPhysChem 5, 998—1002 (2004). 

The early history of the DCC field is coincident with the publication of a series of landmark papers from the Dervan laboratory, describing a code for the design and synthesis of polypyrrole-polyimidazole compounds... 

In another research laboratory, surprised by the lack of success of other research groups and the previous statements about the impossibility of applying biocatalytic chemistry to polithiophenes and polypyrroles, special attention was paid to the enzymatic polymerization of the EDOT monomer [43]. In this case, the first trials succeeded and a blue-colored polymer solution was obtained after 16h of reaction (Scheme 4). As is well-known, an acidic reaction medium is suitable to increase the rate of polymerization. Protonic acids and a variety of Lewis acids catalyze the equilibrium reaction of EDOT to the corresponding dimeric and trimeric compounds without further oxidation or reaction [44]. In this work, three different pHs were evaluated (pH = 2, 4, and 6) in order to establish the optimum for adequate synthesis of EDOT. The UV-visible (UV-Vis) spectra for these three reactions are... 

Bruno FF, Nagarajan R, Roy S, Kumar J, Samuelson LA (2003) Biomimetic synthesis of water soluble conductive polypyrrole and poly(3,4-ethylenedioxythiophene). J Macromol Sci A Pure Appl Chem A 40(12) 1327-1333... 

Electrochemical doping of insulating polymers has been attempted for polyacetylene, polypyrrole, poly-A/-vinyl carbazole and phthalocyaninato-poly-siloxane. Significantly, Shirota et al. [91] claim to have achieved the first synthesis of electrically conducting poly(vinyl ferrocene) by the method of electrochemical deposition (ECD) [91]. This is based on the insolubilization of doped polymers from a solution of neutral polymers. A typical procedure applied [91] for polyvinyl ferrocene is to dissolve the polymer in dichlorometh-ane and oxidize it anodically with Ag/Ag+ reference electrode under selective conditions. The modified polymer [91] (Fig. 28) is a partially oxidized mixed valence salt containing ferrocene and ferrocenium ion pendant groups with C104 as the counter anion. 

An alternative theory associates electron transfer with transfer of a state of aromaticity from molecule to molecule within the stack (77AG(E)519). Efficient charge transport was identified with conversion of a neutral, antiaromatic system to a charged, aromatic radical by electron transfer. This interpretation has been eroded by the synthesis of conductors from aromatic systems such as perylene hexafluoroarsenate (81MI11301) or polypyrrole tetrafluoroborate (80CC397, 81MI11300) where an electron is transferred from a neutral, aromatic molecule to a non-aromatic charged radical. 

Thiophene, pyrrole and their derivatives, in contrast to benzene, are easily oxidized electrochemically in common solvents and this has been a favourite route for their polymerization, because it allows in situ formation of thin films on electrode surfaces. Structure control in electrochemical polymerization is limited and the method is not well suited for preparing substantial amounts of polymer, so that there has been interest in chemical routes as an alternative. Most of the methods described above for synthesis of poly(p-phenylene) have been applied to synthesise polypyrrole and polythiophene, with varying success. 

Shinohara et al.52n suggested that the diffusion rate of dopant ions in polypyrrole films depends upon the size of the anion used as counter-ion in the electrochemical synthesis so that films prepared with CI counter-ions were impermeable to larger ions, at least in the time-scale of a cyclic voltammetry experiment. Tietje-Girault et al. 522) made two-layer polypyrrole films in which a layer was prepared with a large... 

An extensive review of the synthesis of rc-conjugated polymers is presented using a tutorial approach to provide an introduction to the field intended for the undergraduate student and the experienced chemist alike. The many synthetic methodologies that have been used for the synthesis of conjugated polymers are outlined for each class of polymers with a focus on research from the 1990s. The effect of structure on electrical properties is detailed. Specific systems reviewed include the polyacetylenes, polyanilines, polypyrroles, polythiophenes, poly(arylene vinylenes), and polyphenylenes. 

Comparable to thiophene, pyrrole is a five-membered heterocycle, yet the ring nitrogen results in a molecule with distinctly different behavior and a far greater tendency to polymerize oxidatively. The first report of the synthesis of polypyrrole (PPy) 62 that alluded to its electrically conductive nature was published in 1968 [263]. This early material was obtained via electrochemical polymerization and was carried out in 0.1 N sulfuric acid to produce a black film. Since then, a number of improvements, which have resulted from in-depth solvent and electrolyte studies, have made the electrochemical synthesis of PPy the most widely employed method [264-266]. The properties of electrosynthesized PPy are quite sensitive to the electrochemical environment in which it is obtained. The use of various electrolytes yield materials with pronounced differences in conductivity, film morphology, and overall performance [267-270]. Furthermore, the water solubility of pyrrole allows aqueous electrochemistry [271], which is of prime importance for biological applications [272]. 

Diphosphaferrocene, with chromium carbonyls, 5, 220 l,l -Diphospha[2]ferrocenophane, synthesis, 6, 210 Diphosphazanes, in dinuclear Ru complexes, 6, 674 l,l -Diphosphetanylferrocenes, preparation, 6, 200-201 Diphosphine borane complex, polypyrrole support for,... 

Kuwabata S, Kishimoto A, Tanaka T, Yoneyama H. Electrochemical synthesis of composite films of manganese dioxide and polypyrrole and their properties as an active material in lithium secondary batteries. J Electrochem Soc 1994 141 10-15. 

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.)...

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