Charging polymer films

Barendrecht et al. show that the charged polymer films are similar to porous metal... 

Figure 2. Details of methods of charging polymer films that function as electromechanical transducers and also information storage elements.

H. Braun, F. Decker, K. Doblhofer and H. Sotobayashi, The redox-reaction [Fe(CN)6]3 /4 on electrodes coated with fixed charge polymer films - Observation of membrane permeability modulation by the electrode potential, Ber. Bunsenges. Phys. Chem., 1984, 88, 345-350 S-M. Oh and L.R. Faulkner, Luminescent and redox probes of structure and dynamics in quaternized poly(4-viniylpyridine) films on electrodes, J. Am. Chem. Soc., 1989, 111, 5613. 

For the sake of simplicity, we will consider a negatively charged polymer film (negative sites are formed as a result of a reduction process) in contact with a K+A electrolyte. The concentration of the negatively charged sites (X ) is Cx, the value of which depends on the potential according to the Nemst equation. At fixed potential and a concentration of crx, the partitioning equilibrium (y is taken to be 1) is... 

An n-Si electrode was stabilized by coating it with viologen-based polymer films (4) (method Al) Substantial improvements in photocurrent stability were obtained in the presence of electroactive anions, because they are adsorbed by the positively charged polymer film, so providing efficient scavenging of photogenerated holes at the semiconductor surface. 

The electric equilibrium state of an electrode (Me) coated with a fixed-charge polymer film is shown in Fig. The electrolyte is... 

Chen G, Xu Z, Zhang L (2007) Measurement of the surface potential decay of corona-charged polymer films using the pulsed electroacoustic method. Meas Sci Technol 18 1453-1458... 

Rollet, A.L., Porion, P., DelviUe, A., Dial, O., Gebel, G. (2005) Quadrupolar interaction study of various cations confined in porous charged polymer film of sPI ionomers. 

Electrogenerated conducting polymer films incorporate ions from the electrolyte medium for charge compensation (182). Electrochemical cycling in an electrolyte solution results in sequential doping and undoping of the polymer film. In the case of a -doped polymer, oxidation of the film results in the... 

It has been shown that the charge influences the distribution of the primary corrosion products, and recent work has indicated that the existence of carboxyl groups in the polymer film has an important influence on its behaviour when immersed in potassium chloride solutions. 

The kinetic energy of charge earners in a solid increases with increasing temperature and therefore the probability that a charge carrier passes a given potential barrier also increases. The thermally induced current flow of the charge earners from a metal contact into a polymer film can be derived from the Richardson equation, which describes the temperature-induced emission of hot charge carriers from a metal surface... 

The proposed scenario is mainly based on the molecular approach, which considers conjugated polymer films as an ensemble of short (molecular) segments. The main point in the model is that the nature of the electronic state is molecular, i.e. described by localized wavefunctions and discrete energy levels. In spite of the success of this model, in which disorder plays a fundamental role, the description of the basic intrachain properties remains unsatisfactory. The nature of the lowest excited state in m-LPPP is still elusive. Extrinsic dissociation mechanisms (such as charge transfer at accepting impurities) are not clearly distinguished from intrinsic ones, and the question of intrachain versus interchain charge separation is not yet answered. 

Stimulation of the conformational relaxation movements of the polymeric chains (by repulsion between the nascent positive charges), with the generation of free volume. Local nuclei or general and simultaneous relaxation occur, depending on the initial compaction of the polymer film. 

Polymerization at constant current is most convenient for controlling the thickness of the deposited film. Charges of ca. 0.3, 0.2, and 0.08 C cm-2 are required to produce 1 fim of polypyrrole,59 poly(3-methylthio-phene)60 (no data are available for polythiophene), and polyaniline 43 respectively. Although these values can reasonably be used to estimate the thicknesses of most electrochemically formed conducting polymer films, it should be noted that they have considerable (ca. 30%) uncertainties. For each polymer, the relationship between charge and film thickness can... 

The electrochemistry of a polymer-modified electrode is determined by a combination of thermodynamics and the kinetics of charge-transfer and transport processes. Thermodynamic aspects are highlighted by cyclic voltammetry, while kinetic aspects are best studied by other methods. These methods will be introduced here, with the emphasis on how they are used to measure the rates of electron and ion transport in conducting polymer films. Charge transport in electroactive films in general has recently been reviewed elsewhere.9,11... 

Impedance spectroscopy is best suited for the measurement of electronic conductivities in the range 10 -7to 10 2S cm 1.145 In principle, it is perhaps the best method for this range, but it is often difficult to interpret impedance data for conducting polymer films. The charge-transfer resistance can make measurements of bulk film resistances inaccurate,145 and it is often difficult to distinguish between the film s ionic and electronic resistances.144 This is even more of a problem with chronoamperometry146 and chronopotentiometry,147 so that these methods are best avoided. 

It was reabzed early on that because of their high electron transport rates, the charging rates of conducting polymer films would be controlled predominantly by the rate at which charge-compensating ions [Eq.(l)] could be extracted from, or ejected into, the bathing electrolyte solution.160,161 However, these and some other studies employing chronoam-... 

The kinetics of charge transfer between metallic electrodes and conducting polymer films have proved to be difficult to investigate, and little reliable data exist. Charge-transfer limitations have been claimed in cyclic voltammetry, and Butler-Volmer kinetics have been used in a number of... 

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. 

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