Electronically Conducting Organic Polymers

Another limiting factor is that it may not be possible to use some of these electronically conducting organic compounds in aqueous solutions. This is true of the polymer most used in new polymer batteries, polyacetylene, for which an appropriate solvent is propylene carbonate (see Fig. 4.115). 

General Properties of Electronically Conducting Organic Polymers... 

Status of Polypyrrole. Polypyrrole (Diaz, 1981) has been examined and analyzed more than other electronically conducting organic polymers. It is the archetype of this class of compound. 

G. Troch-Nagels, R. Winand and A. Weymeersch and L. Renard, Electron conducting organic coating of mild steel by electropolymerization, J. Appl. Electrochem., 1992, 22, 756 D.E. Tallman, Y. Pae and G.P. Bierwagen, Conducting polymers and corrosion Polyaniline on steel, Corrosion, 1999, 55, 779. 

From what has been written above about ICPs and RPs, it is evident that, in principle, best performance may be reached once the virtues of the two classes of differently conducting polymers are possessed by a single molecule that includes both redox centers and jr-electron conjugated systems typical of ICP chains. Such a coupling is realized in so-called metallopolymers, where redox metal centers are co-ordinated to one or more ligands differently connected to the jt-electron conducting organic backbone [67-79]. 

Figure 1. Time line of the use of electronically conducting organic polymers as electrodes.

Were it possible to develop the promise of electronically conducting organic polymers, an ehnanced horizon would be revealed. Thus, even in the face of oil and natural gas shortages, CO2 could be used as a feedstock by reducing it electrochemically to useful compounds. The prospect for a long term supply of inexpensive, lightweight, non-corrodible electrode materials is hence improved. 

A Structural characteristic of conducting organic polymers is the conjugation of the chain-linked electroactive monomeric units, i.e. the monomers interact via a 7t-electron system. In this respect they are fundamentally different from redox polymers. Although redox polymers also contain electroactive groups, the polymer backbone is not conjugated. Consequently, and irrespective of their charge state, redox polymers are nonconductors. Their importance for electrochemistry lies mainly in their use as materials for modified el trodes. Redox polymers have been discussed in depth in the literature and will not be included in this review. 

Transition metal compounds, such as organic macrocycles, are known to be good electrocatalysts for oxygen reduction. Furthermore, they are inactive for alcohol oxidation. Different phthalocyanines and porphyrins of iron and cobalt were thus dispersed in an electron-conducting polymer (polyaniline, polypyrrole) acting as a conducting matrix, either in the form of a tetrasulfonated counter anion or linked to... 

Metals have a sea of delocalized electrons that are not bound to specific nuclei, and these are responsible for both their high electrical and heat conductivities. Organic compounds do not ordinarily have such delocalized electrons, and are poor electrical and heat conductors. In fact, they are used to coat electrical wires as insulators. If polymers can be made to conduct, then they could be of a great deal of utility, as they are light, can be processed at low temperatures and pressures, and the raw material does not depend on metal mining. However, the possibility of a conducting polymer did not arise till very recent times. 

By contrast, the organic polymers used in lithium batteries have negligible electronic conductivity but are ionic conductors. 

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