Polymer PPI

FIGURE 1.23 Communicating with a conducting polymer PPy/Cl in solution (a) cyclic voltammetry—a plot of current flow versus the electrical (potential) stimulus applied (b) the electrochemical quartz crystal mircobalance readout—mass polymer versus electrical (potential) stimulus applied (c) the resistometry readout—resistance of the polymer versus the electrical (potential) stimulus applied. (Printed with permission from Materials Science Forum, Vol. 189-190, Characterization of conducting polymer-solution interfacial processes using a new electrochemical method, A. Talaie, G. G. Wallace, 1995, p. 188, Trans Tech Publications, Switzerland.)... 

The oxygen reduction reaction (ORR), the importance of which has to be underlined both firom a fundamental point of view and for its implication in electrochemical power sources and in the corrosion of metals [135], has been thoroughly investigated at modified electron conducting polymers. Both metallic particles and transition metal complexes were considered as suitable electrocatalysts for the ORR, and were dispersed in different electron conducting polymers (PPy, PAni, etc). 

Several reviews have been written on this topic [26-27]. That by Tallman et al. in 2002 provides an excellent survey of all the reports up to 2001 concerning PPy, PANI, and PT, and their application to the protection of ferrous and nonferrous metals [27,28]. In addition, they show that many results appear contradictory, a fact they attribute to the variety of experimental conditions. In summarizing this work, they concluded that further investigations are needed for a better understanding of protection mechanisms. Besides, a distinction has to be made between PANI and other polymers (PPy and PT). Although PPy... 

The adherence of the ECP to the metal, in particular when dedoping has occurred, is also extremely important, and critical for good protection, but, unfortunately, is not always specified. A thin passive interlayer firmly anchored to the metal and to the polymer, generally resulting from a precipitation reaction between the metal ion and the doping anion, may improve the adhesion of the material. Of course, this implies a suitable choice of the electrolyte, which will depend both on the monomer and on the metal. Thus, in the following, a distinction will be made between ferrous and nonferrous metals, but also between the most usual conducting polymers (PPy, PANI, PT, and derivatives). 

In this system, MWCNTs not only prevented the volume expansion of the Sn02 particles that are filled into their cavities, but also accommodated the mechanical strain of the lithiated SnO layer coated on the outside wall. The outmost ductile PPy film further served as a restrictive sheath to relieve the volume change and to strengthen the connection between SnO nanoparticles and MWCNTs. Furthermore, as a typical conducting polymer, PPy can guarantee the electrical conductivity of... 

Even though PPy may be used in many application fields, its poor processibility, mechanical, and physical properties have been a large obstacle. To improve the processibility, mechanical and other properties, various kinds of PPy copolymers have been polymerized with many conventional or conducting polymers. PPy was copolymerized electrochemically with polythiophene to improve its disadvantageous properties such as sensitivity to oxygen [47], leading to copolymer films with much less porosity than PPy film (Figure 8.11). 

There is a great supply of p-doping polymers (PPy, PT and derivatives, and polyalkylene dioxythio-phenes) with adequate charge capacity and stability. The development of a new p-doping material is not critical to the development of an EAP-based supercapacitor. 

So, the process for a polypyrrole film in a solution containing CP anions can be envisaged as stated above by Equation 16.1. The oxidized polymer is a gel and the electrons are transferred from, or toward, the metal in contact with the conducting polymer. The oxidized polymer [(PPy" )s(Cl ) (H20)m]gei is a nonstoichiometric compound the Cl content can be increased (or decreased) under control of anodic (or cathodic) charges (ne in Equation 16.1). The electrochemical equipment allows a continuous, reversible, and infinitesimal control of the oxidized material composition (a unique fact related to electromechanical actuators) by the flow of constant anodic or constant cathodic currents (constant charge per time unit), by reversing the direction of the current flow, or by the flow of infinitesimal charges, respectively. 

In a more recent work, Paik et al. described transport properties and stability of sulphonated porphyrin derivatives (3) in films of conducting polymers PPy and PEDOT films using EQCM . As expected, it was evidenced that such anions were not expelled from these polymer films by extensive potential cycles. The authors also analyzed the effects of potential cycling on PEDOT-H2-3 films obtained by two different modes of electropolymerization (i) at a constant current and (ii) with repeated cyclic potential sweeps. Figure 8.2 shows the results of potential cycles in 0.1 M NaCl solution for the two types of films (noted A and B, respectively). In both cases, the general feature of mass increases of the negative... 

In terms of the nanomaterial morphology, specific fabrication methods for five typical conducting polymers (PPy, PANI, PT, PEDOT, PPV) have been reviewed in Sects. 4-8. It deals with nanoparticle, core-shell nanomaterials, hollow nanospheres, nanofibers, nanotubes, nanopatterns, and nanocomposites of each conducting polymer. 

PPy consisting of five-membered heterocylclic rings is one of the most promising conducting polymers. PPy has been extensively explored because of their easy synthesis, tunable conductivity, reversible redox property, and environmental stability. PPy can be easily prepared by chemical or electrochemical polymerization via the oxidation of pyrrole monomers [206]. In general, chemical polymerization leads to intractable powder, whereas electrochemical polymerization results in film deposited on the electrode. 

Insulating matrix polymer/PPy salts (dopant anions S20g , M0O4"-, [PM012O40] -) A potential-driven anion release from the PPy coating that results in an inhibition of the corrosion process taking place in the defect [65]... 

Example 21 Solution Synthesis of a Micellar Water-Soluble Polymer/PPy Composite in Water (Adapted from ref. 67)... 

A modulation of the ionic-gel contraction is possible by electrochemical control of the amount of microcounter ions changed (released and introduced) in conductive polymer (PPy) applying small differences of potential between the two electrodes... 

Fig. 20.40 Illustration of the transition of a polymer (PPy/ROSO. ") film from a cation exchanger to an anion exchanger phase, associated with the progressing electrochemical oxidation of the polymer (from E = -0.5 V to -f-0.5 V). The transition is characterized by a change in sign of the Donnan potential, ROSOi are the dodecyl sulfate ions that constitute practically fixed negative charges. Au is the gold electrode,

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