Electrochemical synthesis polypyrroles

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... 

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]. 

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. 

Electrochemical synthesis of electroconducting polymers such as polyarene [28— 31], polypyrrole [32-34], polythiophene [35], and polyaniline [36, 37] has been carried out in moisture sensitive chloroaluminate ionic liquids. However, the polymer hlms are decomposed rapidly by the corrosive products like HCl generated by hydrolysis of the ionic liquids. In addition the treatment of the chloroalminate ionic liquids requires a special equipment such as glove box. 

The discovery that doped forms of polypyrroles conduct electrical current has spurred a great deal of synthetic activity related to polypyrroles [216-218], Reviews are available on various aspects of the synthesis and properties of polypyrroles [219,220]. In addition, summaries of important aspects of polypyrroles are included in several reviews on electrically conducting polymers [221-226]. Polypyrrole has been synthesized by chemical polymerization in solution [227-231], chemical vapor deposition (CVD) [232,233], and electrochemical polymerization [234-240]. The polymer structure consists primarily of units derived from the coupling of the pyrrole monomer at the 2,5-positions [Eq. (84)]. However, up to a third of the pyrrole rings in electrochemically prepared polypyrrole are not coupled in this manner [241]. 

Pandey, P. C. Singh, G. Srivastava, P. K. Electrochemical synthesis of tetraphenylborate doped polypyrrole and its applications in designing a novel zinc and potassium ion sensor. Electroanalysis. 2002, 14, 427-432... 

Chen, J.H., Huang, Z.P., Wang, D.Z., et al. (2001). Electrochemical synthesis of polypyrrole/carbon nanotube nanoscale composites using weU-aligned carbon nanotube arrays. Appl. Phys. A Mater. Sci. Process, 73, 129-31. 

The preparation of polypyrrole, polythiophene, polyaniline, and related conducting polymers demonstrates principles of electrochemical synthesis that are more widely applicable, and it is instructive to examine these in detail. 

Polypyrroles (PPy s) are formed by the oxidation of pyrrole or substituted pyrrole monomers. In the vast majority of cases, these oxidations have been carried out by either (1) electropolymerization at a conductive substrate (electrode) through the application of an external potential or (2) chemical polymerization in solution by the use of a chemical oxidant. Photochemically initiated and enzyme-catalyzed polymerization routes have also been described but are less developed. These various approaches produce polypyrrole (PPy) materials with different forms—chemical oxidations generally produce powders, whereas electrochemical synthesis leads to films deposited on the working electrode, and enzymatic polymerization gives aqueous dispersions. The conducting polymer products also possess different chemical/electrical properties. These alternative routes to PPy s are therefore discussed separately in this chapter. 

The electrochemical synthesis of a Polypyrrole elastomer blend. This technique allows to obtain thin films which can be easily associated by covulcanization [167],... 

The introduction of sulfonic acid groups in the alkyl side chains affords water-soluble self-doped polypyrrole. Using the sodium salt of the 3-alkylsulfonic acid pyrrole, the monomer acts as electrolyte for the electrochemical synthesis as well. A second long alkyl chain on the opposite side of the pyrrole ring affords a highly ordered lamellar polymer also soluble in chloroform [96]. 

Completely different monomers were called for. Before long, three of today s workhorses had been identified pyrrole, aniline and thiophene. In Japan, Yamamoto [38] and in Germany, Kossmehl [39] synthesized polythiophene doped with pentafluoroarsenate. At the same time, the possibilities of electrochemical polymerization were recognized. At the IBM Lab in San Jose, Diaz used oxidative electrochemical polymerization to prepare polypyrrole [40] and polyaniline. [41] Electrochemical synthesis forms the polymer in its doped state, with the counter-ion (usually an anion) incorporated from the electrolyte. This mechanism permits the selection of a wider range of anions, including those which are not amenable to vapor-phase processes, such as perchlorate and tetra-fluoroborate. Electrochemical doping also overcomes an issue associated with dopants... 

Figure 11.6 SEM images of polypyrrole microcontainers synthesized electrochemical ly using a soap bubble -assisted soft-template method. (Reprinted with permission from Chemical Communications, Electrochemical synthesis of novel polypyrrole microstructures by L. T. Qu and G. Q. Shi, 2003, 2, 206-207. Copyright (2003) Royal Society of Chemistry)...

Figure 12.14 Resistance vs. in-plane magnetic field curves at room temperature for electrodeposited (30 repeats) Co (2 nm)/Cu (3 nm) on conductive polypyrrole film (thickness 5 mm). (Reprinted with permission from Journal of Materials Chemistry, A flexible giant magnetoresistance sensor prepared completely by electrochemical synthesis by F. Van, G. Xue and F. Wan, 12, 2606-2608. Copyright (2002) Royal Society of Chemistry)...

M. Bazzaoui, J.I. Martins, S.C. Costa, E.A. Bazzaoui, T.C. Reis, and L. Martins, Sweet aqueous solution for electrochemical synthesis of polypyrrole Part 2. On ferrous metals, Electrochim. Acta, 51,4516-4527 (2006). 

T. Tiiken, B. Yazici, and M. Erbil, The electrochemical synthesis and corrosion performance of polypyrrole on brass and copper. Prog. Org. Coatings, 51, 152-160 (2004). 

In order to immobilize enzymes in conducting polymers to fabricate biosensors, the electrochemical synthesis of polypyrrole films was studied under different conditions. It was found that the size and morphology of polypyrrole films synthesized using cyclic voltammetry were affected by the concentration of the supporting electrolyte at a scan potential range between 0.0 and 1.0 V (vs. SCE), and at a scan rate of 48 mV s [47]. The diameters of particles prepared in a solution containing 0.10 M pyrrole and 0.10 M NaCl... 

The fabrication of polypyrrole wires via electropolymerization within poly(methyl methacrylate) nanochannels on an indium tin oxide (ITO) substrate was reported by Chen et al. [53]. The electrochemical synthesis of polypyrrole was performed by a cyclic voltammetry method in aqueous 0.1 M NaC104 containing 0.1 M pyrrole monomer. The potential was scanned 10 times between -0.7 and +0.6 V vs. Pt at a scan rate of 100 mV s . The nanochannels act as templates for electropolymerization of polypyrrole nanowires. 

Figure 17.6 FESEM images of polypyrrole nanofIber network (a) Low magnification image and (b) edge view of the polypyrrole nanofiber network. High magnification images of polypyrrole nanofiber network formed at (c) 120 s and (d) 1 b. (Reprinted with permission from Macromolecules, Template-Free Electrochemical Synthesis of Superhydrophilic Polypyrrole Nano fiber Network by J.F. Zhang, C. M. Li, S.J. Baoetal.,41, 19, 7053-7057. Copyright (2008) American Chemical Society)...

J.M. Chen, S.W. Liao, and Y.C. Tsai, Electrochemical synthesis of polypyrrole within PMMA nanochannels produced by AFM mechanical lithography, Synth. Met., 155, 11-17 (2005). 

R.A. KhaUdiali, Electrochemical synthesis and characterization of electroactive conducting polypyrrole polymers, Russ. J. Electrochem., 41(9), 1023-1935 (2005). 

Polypyrrole and many of its derivatives can be synthesized via simple chemical or electrochemical methods [120]. Photochemically initiated and enzyme-catalyzed polymerization routes have also been described but less developed. Different synthesis routes produce polypyrrole with different forms chemical oxidations generally produce powders, while electrochemical synthesis leads to films deposited on the working electrode and enzymatic polymerization gives aqueous dispersions [Liu. Y. C, 2002, Tadros. T. H, 2005 and Wallace. G. G, 2003]. As mentioned above the electrochemical polymerization method is utilized extensively for production of electro active/conductive films. The film properties can be easily controlled by simply varying the electrolysis conditions such as electrode potential, current density, solvent, and electrolyte. It also enables control of thickness of the polymers. Electrochemical synthesis of polymers is a complex process and various factors such as the nature and concentration of monomer/electrolyte, cell conditions, the solvent, electrode, applied potential and temperature, pH affects the yield and the quality of the film... 

Lin, E.-R, Chiu, C.-J., and Tsai, Y.-C. [2014]. One-step electrochemical synthesis of polypyrrole-graphene-glucose oxidase nanobiocomposite for glucose sensing, J. Electrochem. Soa, 161, pp. B243-B247. 

N. P. Gaponik, D. V. Talapin, A. L. Rogach, A. Eychmiiller, Electrochemical Synthesis of CdTe Nano crystal/Polypyrrole Composites for Optoelectronic Applications. /. Mater. Chem. 2000,10, 2163-2166. 

Yoneyama H., Shoji Y, and Kawai K., Electrochemical synthesis of polypyrrole films containing metal oxide particles, Chem. Lett, 1989, 1067-1070. 

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