Electrical properties electrically conductive polymers

Chemical and Biochemical Sensors. The sensitivity of the electrical properties of conductive polymers to chemical stimuli suggests they may prove useful in a number of sensing applications. 

Chain length is another factor closely related to the structural characterization of conducting polymers. The importance of this parameter lies in its considerable influence on the electric as well as the electrochemical properties of conducting polymers. However, the molecular weight techniques normally used in polymer chemistry cannot be employed on account of the extreme insolubility of the materials. A comparison between spectroscopic findings (XPS, UPS, EES) for PPy and model calculations has led some researchers to conclude that 10 is the minimum number of monomeric units in a PPy chain, with the maximum within one order of magnitude n9- 27,i28) mechanical qualities of the electropolymerized films,... 

In this context numerous changes were made. The chapter Properties of Polymers was revised and a new section Correlations of Structure and Morphology with the Properties of Polymers was added. The chapter Characterization of Macromolecules was revised and enlarged. 15 examples have been deleted as they did no longer represent the state of the art and/or were of minor educational value. Several new experiments (plus background text) were added, as, for example controlled radical polymerization - enzymatic polymerization - microemulsions - polyelectrolytes as superabsorbants - hyperbranched polymers - new blockcopolymers - high impact polystyrene - electrical conducting polymers. 

In order to satisfy the industrial demand, the performance of supercapacitors must be improved and new solutions should be proposed. The development of new materials and new concepts has enabled important breakthroughs during the last years. In this forecast, carbon plays a central role. Due to its low cost, versatility of nanotextural and structural properties, high electrical conductivity, it is the main electrode component. Nanoporous carbons are the active electrode material, whereas carbon blacks or nanotubes can be used for improving the conductivity of electrodes or as support of other active materials, e.g., oxides or electrically conducting polymers. 

The discovery that doped forms of polypyrroles conduct electrical current has spurred a great deal of synthetic activity related to polypyrroles [216-218], Reviews are available on various aspects of the synthesis and properties of polypyrroles [219,220]. In addition, summaries of important aspects of polypyrroles are included in several reviews on electrically conducting polymers [221-226]. Polypyrrole has been synthesized by chemical polymerization in solution [227-231], chemical vapor deposition (CVD) [232,233], and electrochemical polymerization [234-240]. The polymer structure consists primarily of units derived from the coupling of the pyrrole monomer at the 2,5-positions [Eq. (84)]. However, up to a third of the pyrrole rings in electrochemically prepared polypyrrole are not coupled in this manner [241]. 

Toward an understanding of the conduction properties of polythiophenes (26) and polypyrroles (25) a large number of soluble oligomers has been prepared. Oligothiophenes, indeed, represent the most common model compounds for electrically conducting polymers [149]. Thereby, lower oligomers... 

Electrically conducting polymers combine the optical and electronic properties of inorganic semiconductors with the processing ease of conventional polymers. Their structures are continuations of the 1,3-butadiene structure to greater lengths, and the electronic structure for the individual molecule is described by bands. These polymers are made electrically conducting by doping. 

Waltman, R. J. Bargon, J. Electrically conducting polymers a review of the electropolymerization reaction, of the effects of chemical structure on polymer film properties, and of applications towards technology. Canad. J. Chem. 1986, 64, 76-95... 

When the two tables are compared it is evident that there is a wide choice in fillers which either enhance or retain dielectric properties of polymers. It is more difficult to formulate conductive polymers where consideration must be given to how the filler can change properties of the polymer. Electrically conductive polymers can be divided into three groups ... 

The state of the art is such that an understanding of these processes is now well established, and an exciting fertile field lies before intelligent material research scientists. We can, by design, control the chemical and electrical properties of conducting polymers at the point of assembly. How these properties are likely to vary as a result of application of external stimuli can also be manipulated by the synthesis process. 

Another interesting application that uses the dynamic properties of conducting polymers is electrochromic devices.44,45 46 47 An electrochromic device based on polypyrrole is shown in Figure 1.8. The polypyrrole changes from colorless to black when it is oxidized by the application of positive potentials. Similarly, polythiophene and polyaniline undergo distinct color changes when an electrical potential is applied. 

Recent applications of SPM techniques have revealed new details of the electrical properties of conducting polymers. In one example, STM images were taken of the granular structure of electrochemically prepared polyaniline films. Simultane-... 

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