Electronically conductive polymers charge transport

This article addresses the synthesis, properties, and appHcations of redox dopable electronically conducting polymers and presents an overview of the field, drawing on specific examples to illustrate general concepts. There have been a number of excellent review articles (1—13). Metal particle-filled polymers, where electrical conductivity is the result of percolation of conducting filler particles in an insulating matrix (14) and ionically conducting polymers, where charge-transport is the result of the motion of ions and is thus a problem of mass transport (15), are not discussed. 

Charge transfer kinetics for electronically conducting polymer formation, 583 Charge transport in polymers, 567 Chemical breakdown model for passivity, 236... 

Van Dyke L S, Martin C R (1990) Fibrillar electronically conductive polymers show enhanced rates of charge transport. Synth Met 36 275-281... 

Note 3 Unlike polymeric electrolytes, in which charge is transported by dissolved ions, charge in intrinsically conducting polymers is transported along and between polymer molecules via generated charge carriers (e.g., holes, electrons). 

Conductivity in conjugated polymers was discovered several decades ago [1]. Since then, there has been major advances in the synthesis, characterization and applicability of conjugated polymers for different device applications. They all have in common a conjugated bond structure that allows for electron delocalization and charge transport along the polymer backbone resulting in unique electrical, optical and magnetic properties. Molecular structures for some commonly used CPs are shown in Fig. 7.1. 

Depending on the type of charge transport carrier, conductive polymers can be classified into two main groups of ionically and electronically conductive polymers (Fig. 6.1). Polyethylene oxide with lithium perchlorate (LiCl04) is an example of an... 

Penner, R. M., and Martin, C. R., Electrochemical investigations of electronically conductive polymers. 2. Evaluation of charge-transport rates in polypyrrole using an alternating current impedance method, J. Phys. Chem., 93, 984-989 (1989). 

In addition, we have recently described a procedure for controlling the morphologies of electronically conductive polymers (32). This procedure involves the electrochemical growth of the conductive polymer at an electrode surface which has been masked with a microporous polymer membrane. The pores in this membrane act as templates for the nascent electronically conductive polymer. Because the template membrane contains linear cylindrical pores, cylindrical conductive polymer fibrils are obtained (32). We will show in this manuscript that microfibrillar polypyrrole films prepared via this approach can support higher rates of charge-transport than conventional polypyrrole. 

We have developed a new small amplitude electrochemical method for determination of apparent diffusion coefficients associated with charge-transport in electronically conductive polymers. For the reasons noted in the Theory Section, this method is ideally suited for investigations of such pol3rmers. In a more general sense, this method should also be a convenient and powerful tool for studying transport in nearly any type of electroactive polymer film. Some of the features which make this an attractive and powerful method for analysis of transport in polymer films are discussed below. 

FIGURE 1.17. Charge transport processes (microscopic and macroscopic) in electronically conducting polymers. 

We have outlined the synthesis, structural characterization, spectroscopic and electronic features, and charge transport properties as well as electronic device applications of the molecular conductive materials of polythiophenes and oligothiophenes. These materials have been characterized and described as those comprising thiophene ring units and were shown to exhibit unique structural and electronic properties as a function of the number of those units (oligomer to polymer). 

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