Conducting polymers electrochemical behavior

The presence of polymer, solvent, and ionic components in conducting polymers reminds one of the composition of the materials chosen by nature to produce muscles, neurons, and skin in living creatures. We will describe here some devices ready for commercial applications, such as artificial muscles, smart windows, or smart membranes other industrial products such as polymeric batteries or smart mirrors and processes and devices under development, such as biocompatible nervous system interfaces, smart membranes, and electron-ion transducers, all of them based on the electrochemical behavior of electrodes that are three dimensional at the molecular level. During the discussion we will emphasize the analogies between these electrochemical systems and analogous biological systems. Our aim is to introduce an electrochemistry for conducting polymers, and by extension, for any electrodic process where the structure of the electrode is taken into account. 

Most of the models developed to describe the electrochemical behavior of the conducting polymers attempt an approach through porous structure, percolation thresholds between oxidized and reduced regions, and changes of phases, including nucleation processes, etc. (see Refs. 93, 94, 176, 177, and references therein). Most of them have been successful in describing some specific behavior of the system, but they fail when the... 

As illustrated in the previous sections, the electrochemical properties of conducting polymer films are strongly influenced by polymer-ion interactions. These interactions are in turn influenced by the nature of the solvent and the solvent content of the film. Consequently, the electrochemical behavior of conducting polymer films can be highly solvent dependent. Films can even become electrochemically inactive because of lack of solvation.114,197... 

The conducting polymers show a significant non-faradaic component of the electrochemical mechanism. The essential differences of faradaic and non-faradaic systems in equilibrium behavior, trends of galvanostatic charge - discharge curves and cyclic voltammograms have been shown, and criteria for the identification of these mechanisms are proposed [8],... 

In this paper we describe the preparation of thin polymer films by surface catalysis and anodic deposition. The results indicate that both synthesis routes produce orientationally ordered films that have similar infrared spectra. It is also shown that thin ordered films of poly(thiophene) have different electrochemical behavior than the fibrous films that are electrically conducting. 

Self-doped PANI are very interesting due to their unique electrochemical behavior unlike PANI, the self-doped polymer remains in its doped state in near neutral or alkaline media [28]. Fully self-doped PANIs are not easy to synthesize due to the lower reactivity of acid-functionalized anilines. Kim et al. [29, 30] introduced an alternative approach in the template-assisted enzymatic polymerization of aniline. Previously, only polyanionic templates had been used for PANI synthesis. However, acid-functionalized anilines bear a net anionic charge in aqueous solution, and attempts to use SPS as template with carboxyl-functionalized aniline resulted in red-brown colored polymers with no polaron transitions, regardless of the synthetic conditions. The use of polycationic templates, such as those shown in Figure 8.2 allowed the synthesis of linear and electrically conductive PANIs with self-doping ability due to the doping effect of the carboxyl groups present in the polymer backbone. 

Chapter 13 was largely concerned with adsorbed species that are not electroactive. In this chapter we consider electroactive monolayers and thicker films on conductive substrates these are frequently called chemically modified electrodes. This area of electrochemistry has been a very active one in recent years, and a number of reviews discussing the preparation, characterization, and electrochemical behavior of chemically modified electrodes are available (1-14). These electrodes are often prepared by the modification of a conductive substrate to produce an electrode suited to a particular function, whose properties are different from those of the unmodified substrate. Modified electrodes can be prepared in several different ways, as discussed in vSection 14.2, including irreversible adsorption, covalent attachment of a monolayer, and coating the electrode with films of polymers or other materials. 

Electronically conducting polymers possess a variety of properties related to their electrochemical behavior and are therefore active materials whose properties can be altered as a function of their electrochemical potential. The importance and potential impact of this new dass of material was recognized by the world scientific community when Hideki Shirakawa, Alan J. Heeger and Alan G. MacDiarmid were awarded the Nobel Prize in Chemistry in 2000 "for the discovery and development of electronically conductive polymers". 

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