Conjugated conducting polymers Polythiophene

CLASS Polyheterocyclics conjugated conducting polymers STRUCTURE Polythiophene exists in two structures (Aromatic)... 

Poly 1 -(trimethylsilyl)-1 -propynel Conjugated conducting polymers Polypyrrole Polythiophene... 

Solitons are considered to be important defect states in these conjugated polymers (see Fig. 6.48). It has however been shown that correlation energy is the more important factor in giving rise to the energy gap in (CH) (Soos Ramasesha, 1983). Other polymers related to polyacetylene are polythiophene, polypyrrole, poly-phenylenesulphide, and polyparaphenylene (Section 3.3). Extensive measurements on doped polyacetylenes have been reported in the last five years and these materials, unlike other conducting polymers such as (SN), seem to have good technological potential. 

Against this background of infusible conducting polymers, the development of the soluble polythiophenes is most interesting. Glass transition temperatures have been reported as 48 °C for poly(3-butylthiophene) and 145 °C for poly(3-methyl-thiophene) 261). These polymers also show crystallinity in films and can be crystallized from solution. Solution studies indicate that there are two chain conformations 262) and the availability of a non-conjugated conformation may be a key to the low transition temperatures and solubility, when compared to the stiff-chain conjugated polymers. 

Keywords Conducting polymers, Conjugated polymers, Polyacetylenes, Polyanilines, Polypyrroles, Polythiophenes, Poly(arylene vinylenes), Polyphenylenes... 

Although the original research on conductive polymers was done with polyacetylene, a number of other conjugated polymers have been developed for such uses. Among these products are the polythiophenes, polyanilines, polyphenylenevinylenes, polyethylene-dioxythiophenes, polypyrroles, and polydialkylfluorenes. These products are now beginning to find applications in a number of industrial, research, medical, and consumer devices. 

Conjugated Polythiophenes. Because of their potential electrical conductivity, conjugated polythiophenes, along with other conjugated polymeric systems, have been extensively studied since the pioneering works in the early 1980s (65,66) (see Electrically conductive polymers). 

Many other air-stable conducting polymers followed (Fig. 12.10) polypyrrole, polythiophene, polyaniline (which had been known since the nineteenth century as "aniline black"), and so on (Table 12.4). These polymers are semiconducting, not metallic, when "doped" with electron donors or acceptors the individual conjugated chains have finite length, so the conductivity is limited by chain-to-chain hopping. Also, if the individual strands exceed four or so oligomers, the conjugation tends to decrease, as the strand tends to adopt a screw-type distortion. The transport within each strand is attributed to polarons and bipolarons. 

The electrochemical properties of conductive polymer systems are important with regard to understanding the electrochemical doping process and in applications of conductive polymers as battery electrodes. We have developed a computational method, based on the Valence Effective Hamiltonian technique, which is remarkably effective in the computation of oxidation and reduction potentials of a variety of conjugated polymers (polyacetylene, polyphenylene, polythiophene, polypyrrole) and their oligomers. 

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