Charge-controllable conducting polymer

Anionic polyelectrolytes (PE), such as potassium poly-(vinyl-sulphate) (PVSK), (sodium poly(styrene-4-sulphonate) (PSSNa) and Nafion, were incorporated in conducting polymer according to the same procedure as described above, and charge-controllable conducting polymer membranes were obtained [15-17]. 

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... 

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 diffusion of dopants into, and out of, conducting polymers is important for possible applications in batteries, and as conductors or semiconductors. For conductors or semiconductors, the chief requirements are that the material can be doped in a reasonable time, but that it will then not lose dopant over periods of years. This is particularly important in determining junction stability in devices. In the case of batteries, on the other hand, rapid and reversible uptake and loss of dopants is needed, since the diffusion rate controls charging and discharging rates. In addition, the accessibility of the structure to oxygen, and other degradants, will be a factor in the stability of the polymer. 

The thickness of the PPy-film has an effect on the response of the electrode towards the substrate, and can be controlled by the amount of charge passed through the system during synthesis of the conducting polymer. As can be seen in Table I, the response of the electrode to BNAH (slope of the calibration curve) increases with the thickness of the film up to about three Coulombs of charge passed. If thicker layers are deposited the response is only slightly lowered. This suggests that the transport of electrons from the (reduced) flavin to the electrode does not depend upon the diffusion of a reactive species (H to the platinum surface, which would limit the current as the film thickness is increased. 

The modification of electrode surfaces with electroactive polymer films provides a means to control interfacial characteristics. With such a capability, one can envisage numerous possible applications, in areas as diverse as electronic devices, sensors, electrocatalysis, energy conversion and storage, electronic displays, and reference electrode systems [1, 2]. With these applications in view, a wide variety of electroactive polymeric materials have been investigated. These include both redox polymers (by which we imply polymers with discrete redox entities distributed along the polymer spine) and conducting polymers (by which we imply polymers with delocalised charge centres on the polymer spine). 

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