Electronically conducting polymer

1 Lithium-Doped Conducting Polymer and Lithium-Polymer Batteries 

More recently, attention has been focused on polyheterocycles. In the typical case of a cell based on a PPy cathode, a LiC104-PC electrolyte and a lithium metal anode, the electrochemical process can be written as  

It is interesting to use the polymer cathodes in lithium-ion cell types. This concept has been exploited by assembling cells having the structure C/LiC104-EC-PC-PMMA/PPy. 

Laboratory prototypes have been fabricated by preparing the electrodes in the form of thin films backed on metallic substrates and separating them by the polymer electrolyte membrane [142, 143]. By charging the cell, Locations enter the graphite structure and C104 anions simultaneously inject into the PPy structure  

The results reported above indicate that a proper choice of the battery components enables the intrinsic potentialities of the polymer electrode and electrolyte materials to be exploited for the development of revolutionary electrochemical devices. Accordingly, a number of laboratories are currently seeking to enhance the electrochemical properties of conducting polymers by designing suitable materials, the final goal being to optimise their response in advanced, plastic-like batteries. Undoubtedly, this will be the type of batteries that will dominate the electronic market in the new millennium. 

Most conducting polymers, such as doped poly(acetylene), poly(p-pheny-lene), and poly(/ -phenylene sulfide), are not stable in air. Their electrical conductivity degrades rapidly, apparently due to reaction with oxygen and/or water. Poly(pyrrole) by contrast appears to be stable in the doped conductive state. 

Polymers for these conductive systems may be synthesised by a variety of means including Ziegler-Natta polymerisation or nucleophilic displacement reactions. The molecules tend to be rigid because of the need for them to possess extended conjugation. This lack of free rotation about carbon-carbon bonds within the molecule imposes a high energy barrier to solvation, thus making these molecules difficult to dissolve. This lack of solubility in turn 

There are difficulties in analysing conductive polymers, and information on the relationship between structure and properties somewhat difficult to obtain. These materials have already found a variety of uses, including flat panel displays, antistatic packaging and rechargeable batteries, and other applications are likely to emerge in the future. 

Finally, synthetic metals made of polymeric organic molecules may also show the property of ferromagnetism. Organic materials of this kind were first demonstrated in 1987 by Ovchinnikov and his co-workers at the Institute of Chemical Physics in Moscow. The polymer they used was based on a polydiacetylene backbone, which contains alternating double-single and triple-single bonds between the carbon atoms of the molecule (10.2). 

This highly conjugated molecule was stabilised with nitroxyl biradical side chains. The resulting material had sufficient ferromagnetism that a usable compass needle could be made from it. Despite the success of this demonstration, organic ferromagnetism remains a curiosity. Such polymers are not likely to replace conventional ferromagnetic metals in any application within the foreseeable future. 

Guimard et al. [74] have carried out a very detailed review on developments in electrically conducting polymers, particularly in the field of biomedical engineering. 

Polymers that, to date, have been investigated for their electrical conducting properties include polypyrrole, polyaniline, polythiophene, and polymer nanotube composites. The advantages of conducting polymers include good conductivity, biocompatibility, good stability, low impedance ability to entrap molecules, efficient charge transfer, and ability to entrap biomolecules. 

Licsea-Claverie, F.J.U. Larrillo, A. Avarez-Castillo, and V.M. Castano, Composites. 1999,20,314. 

Barysiak, K. Vandervelde, J. Garbarczyk, and J.K. Krucinska, Fibres and Textiles in Eastern Europe, 2004, 12, 64. 

Kusman, M. Ishak, W.J. Chan, and T. Taleishi, European Polymer Journal, 2008, 44, 102. 

FIGURE 1.17. Charge transport processes (microscopic and macroscopic) in electronically conducting polymers. 

Doping Processes, Charge Carriers, and Conduction in Electronicaily Conducting Polymers 

The partial oxidation of the polymer chain is termed p-doping. The basic process involves removing electrons to form a positively charged repeat unit 

The mobile dopant obeys the following diffusion/reaction equation  

The pertinent initial and boundary conditions are at time t = 0 and for 0 c L, 0 = 0, furthermore for / 0 at c = 0 daldx = 0 and a = a°° at X = L, where we assumed that species A is present in the external phase at a bulk concentration a and the partition coefficient is unity. We further assume that there is no kinetic barrier at the film/solution interface to the passage of dopant A into the film. 

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This article addresses the synthesis, properties, and appHcations of redox dopable electronically conducting polymers and presents an overview of the field, drawing on specific examples to illustrate general concepts. There have been a number of excellent review articles (1—13). Metal particle-filled polymers, where electrical conductivity is the result of percolation of conducting filler particles in an insulating matrix (14) and ionically conducting polymers, where charge-transport is the result of the motion of ions and is thus a problem of mass transport (15), are not discussed. 

Conducting Polymers Electronically conducting polymers (such as polypyrrole, polythiophene, and polyaniline) have attracted considerable attention due to their ability to switch reversibly between the positively charged conductive state and a neutral, essentially insulating, form and to incorporate and expel anionic species (from and to the surrounding solution), upon oxidation or reduction ... 

Pickup, P. G. Electrochemistry of Electronically Conducting Polymer Films 33... 

Charge transfer kinetics for electronically conducting polymer formation, 583 Charge transport in polymers, 567 Chemical breakdown model for passivity, 236... 

Electron transfer mechanism Butler-Volmer kinetics and, 587 in electronically conducting polymers, 568... 

Impedance, for measurement of the potential of zero charge, 35 Impedance blocks, for polypyrrole, 577 Impedance spectroscopy of electronically conducting polymers, 576 Indium... 

Quantum chemical calculations, 172 Quantum chemical method, calculations of the adsorption of water by, 172 Quantum mechanical calculations for the metal-solution interface (Kripsonsov), 174 and water adsorption, 76 Quartz crystal micro-balance, used for electronically conducting polymer formation, 578... 

This volume contains six chapters and a cumulative index for numbers 1-33. The topics covered include the potential of zero charge nonequilibrium fluctuation in the corrosion process conducting polymers, electrochemistry, and biomimicking processes microwave (photo)-electrochemistry improvements in fluorine generation and electronically conducting polymer films. 

The final chapter, by Peter Pickup of Memorial University of Newfoundland, gives a comprehensive account of the major and rapidly developing field of the electrochemistry of electronically conducting polymers and their applications. Following the discovery of these materi-... 

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