Polyacetylene-polypyrrole

The concept of electrochemical intercalation/insertion of guest ions into the host material is further used in connection with redox processes in electronically conductive polymers (polyacetylene, polypyrrole, etc., see below). The product of the electrochemical insertion reaction should also be an electrical conductor. The latter condition is sometimes by-passed, in systems where the non-conducting host material (e.g. fluorographite) is finely mixed with a conductive binder. All the mentioned host materials (graphite, oxides, sulphides, polymers, fluorographite) are studied as prospective cathodic materials for Li batteries. 

Metallic conduction has recently been observed in specially-prepared organic compounds, such as polyacetylene, polypyrrole, and polyaniline, having conductivities of the order 10 9 (ohm-cm)1 but by proper doping these conductivities can be increased to 102 (ohm-cm)-1. Some of the organic metallic systems have also been converted into the superconducting state by proper doping, but in all cases the Tc remains at very low temperature. 

Electrochemical doping of insulating polymers has been attempted for polyacetylene, polypyrrole, poly-A/-vinyl carbazole and phthalocyaninato-poly-siloxane. Significantly, Shirota et al. [91] claim to have achieved the first synthesis of electrically conducting poly(vinyl ferrocene) by the method of electrochemical deposition (ECD) [91]. This is based on the insolubilization of doped polymers from a solution of neutral polymers. A typical procedure applied [91] for polyvinyl ferrocene is to dissolve the polymer in dichlorometh-ane and oxidize it anodically with Ag/Ag+ reference electrode under selective conditions. The modified polymer [91] (Fig. 28) is a partially oxidized mixed valence salt containing ferrocene and ferrocenium ion pendant groups with C104 as the counter anion. 

In considering the potential applications of electroactive polymers, the question always arises as to their stability. The deterioration of a physical property such as conductivity can be easily measured, but the chemical processes underlying it are not as easy to be revealed. In order to understand them, XPS has been used to follow the structural changes which occur in the polymer chain and the counter-ions of the doped polymer. The following sections present some XPS findings on the degradation of electroactive polymers, such as polyacetylene, polypyrrole, polythiophene and polyaniline, in the undoped and doped states. 

The formation of conductive conjugated polymers [e.g., polyacetylene, polypyrrole, polythiophene, polyaniline and poly(p-phenylene)] [92, 94] on electrodes by electropolymerization has been studied thoroughly [95]. If the electropolymerization is performed in a solution containing both the monomer and enzyme, then enzymes present in the immediate vicinity of the electrode surface become trapped in the... 

The choice of counterion (anion or cation) has a major effect on the stability of conducting polymers. The stability of donor- (36) and acceptor-doped (37, 38) polyacetylenes, polypyrrole (39), poly(alkylthiophene)s (40), and other polymers (40) has been studied by using thermogravimetric anal-... 

Conducting polymers such as polyacetylene, polypyrrole, polyaniline, polythiophene, etc. have been actively studied for use in various fields due to their interesting properties batteries,46 electrochromic displays,47 materials for supercapacitors,48 corrosion protection,49 protecting layers for static electricity,50 materials for organic electroluminescence displays,51 sensing materials,52 etc. Polypyrrole is reported to be extremely rigid, with a semi-crystalline structure. 

In contrast to polyacetylene, polypyrrole has high mechanical and chemical stability and can be produced continuously as flexible film (thickness 80 fjm, tradename Lutamer, BASF) by electrochemical techniques [14]. 

The typical conjugated polymers (CPs] with conjugated chain structures include polyacetylene, polypyrrole (PPy], polythiophene (PTh], polyaniline (PANl] and their derivatives.The conjugated structures exhibit strong UV-Vis absorptions in visible... 

From the beginning of their history in the late 1970s, conductive polymers (organic metals) have been considered as intractable and insoluble. It was an important goal in basic research as in application-oriented materials science to develop techniques by which they could be processed. The use of solvents was one of the options. As early as 1983-84, after five years of research, we happened to create the first clear dispersions of polyacetylene, polypyrrole, and polyaniline [42], with and without the presence of conventional polymeric binders. This was the beginning of nanotechnology with organic metals. 

Direct dispersion of a fully polymerized, washed, and dried OM powder (e.g., polyacetylene, polypyrrole, polyaniline, etc., today exclusively practiced with PAni) in a polymer matrix. The first realization of this concept was published by us in 1984 [51] improvements based on a new technology for the polymerization of dispersible OM powders were later realized in 1987 [53]. The technology described in Ref. [51] and Ref. [53] and in further improvement patents is independent of whether one is preparing a nanoparticulate dispersion in a polymer matrix or in a solvent, or with the help of solvents in a polymer matrix. 

Activated carbons are also adequate supports for HPA since the acidity of the heteropoly compounds is preserved [P3j. In the case of microporous carbons the HPA will be deposited on the external surface. However, in any support, if liquid phase processes are used, leaching of the supported HPA can be a serious problem [37]. Conjugated polymers such as polyacetylene, polypyrrole and polyaniline have been used as HPA supports. In the case of polyacetylene the HPA can be introduced on the surface of the polymer, while retaining its acidity [38]. However, unless a very special behaviour could be achieved, this will nor be able to compete with other less expensive inorganic supports. 

It has been shown that conjugated polymers, such as polyacetylene, polypyrrole and polyaniline can be doped with heteropolyanions of Keggin structure. They constitute a new type of catalytic support at which catalytically active species are dispersed on the molecular scale. 

More recently, an all-polymer battery based on derivatized polythiophenes supported on graphite-coated supports was described (139). In this instance, polythiophene functioned more effectively in the n-doping region and provided an improved cell discharge voltage of 2.4 V and capacities of 9.5-1.5 mAh g. A recent approach is the development of a polymer/polsrmer battery based on polyaniline anode and poly-l-naphthol cathode (140). This device has been reported with an impressive cell voltage of 1.4 V, a specific capacity of 150 Ah g, and a loss of 15% of cell capacity after 100 cycles. Other attempts at fabricating battery systems have been made (141) with polyacetylene, polypyrrole, and polyanibne (142),... 

In contrast to polyacetylene, polypyrrole is exceptionally stable and can be quite easily produced continuously by electrochemical techniques (Figure 3.13). Some general considerations apply to the choice of... 

Polymers. Electronically conductive polymers may also be used as cathode materials in rechargeable lithium batteries. The most popular polymers are polyacetylene, polypyrrole, polyaniline, and polythiophene, which are made conductive by doping with suitable anions. The discharge-charge process is a redox reaction in the polymer. The low specific energy, high cost, and their instability, however, make these polymers less attractive. They have been used in small coin-type batteries with a lithium-aluminum alloy as the anode. 

The reduction of an organic polymer. The polymer which has been most successful is poly(carbon monofluoride) (CF) which can be manufactured as a high surface-area powder capable of being reduced at a high rate at a very positive potential. Oxidized polyacetylene, polypyrrole and polyaniline are other polymers which have been discussed. 

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