Polyacetylene polymers

Polyacetylenes. The first report of the synthesis of a strong, flexible, free-standing film of the simplest conjugated polymer, polyacetylene [26571-64-2] (CH), was made in 1974 (16). The process, known as the Shirakawa technique, involves polymerization of acetylene on a thin-film coating of a heterogeneous Ziegler-Natta initiator system in a glass reactor, as shown in equation 1. 

Acetylene (ethyne), C2H2, can be polymerized, (a) Draw the Lewis structure for acetylene and draw a Lewis structure for the polymer that results when acetylene is polymerized. The polymer has formula (CH), where n is large, (b) Consider the polymers polyacetylene and polyethylene. The latter has the formula (CH2)W and is an insulating material (plastic wrap is made of polyethylene), whereas polyacetylene is a darkly colored material that can conduct electricity when properly treated. On the basis of your answer to part (a), suggest an explanation for the difference in the two polymers. 

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. 

The relatively high electronic conductivity of conducting polymers is connected with the presence in polymers of internal system of poly-7t-conjugated bonds. This is easy to understand on the example of a simplest type of conducting polymer (polyacetylene) in the main and activated states (Figure 6). 

The e. s. r. and conductivity of polymers such as the polyacene/qui-none radical polymers (PAQR polymers), polyacetylenes and polybenzimidazoles have been investigated (59, 60, 61). The term eka conjugated has been coined to decribe their properties which are very similar to those previously described. The e. s. r. signal is without structure, the activation energy which ranges from 0.2—2.0 ev is considerably... 

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

Instead of bemoaning the error, Shirakawa decided to learn more about this fascinating new version of an old familiar polymer, polyacetylene. He soon discovered that the silvery film consisted of the trans form of polyacetylene and that a comparable copper-colored film could he produced with large quantities of catalyst at different temperatures. The copper-colored film was found to consist of the cis form of the polymer. 

Like many other organic conducting polymers, polyacetylene is electrochemically active, attracting a great deal of interest both from the scientific and the applied point of view. In the year 2000 the chemistry Nobel Prize was granted to A. J. Heeger, H. Shirakawa, and A. G. MacDiarmid for their work on polyacetylene and the nature of conducting polymers. 

In the examples of our work on organic molecular and polymeric solids that follow, first some contributions to the UPS line widths in condensed molecular solids are discussed for two prototype systems, anthracene and isopropyl benzene then the UPS of two.aromatic pendant group polymers, polystyrene and poly(2-vinyl pyridine), are discussed and compared with some spectra concerning the simplest linear conjugated polymer, polyacetylene. 

Unlike vinyl polymers, polyacetylenes which have alternating double bonds along the main chain often show the following unique properties i) electrical conductivity (semiconductivity), ii) paramagnetism, iii) chain stiffness, iv) geometrical isomerism, and v) color. Thus it seems interesting to elucidate the properties of polyacetylenes and develop their functions. 

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. 

The first study of spin dynamics in a conducting polymer, polyacetylene doped with AsFb, was reported by Ncchtschein et al. in 1980, as shown in Figure 6.52 [143]. With (6.14) assuming cj>... 

In 1977, the first covalent organic polymer, polyacetylene (CH), , that could be doped through the semiconducting to the metallic range, was reported. Another significant breakthrough occurred in 1980 with the discovery that PPP could be doped to conductivity levels quite comparable to those in polyacetylene. This polymer is the first example of non-acetylene hydrocarbon polymer that can be doped to give polymers with metallic properties. 

The first conducting polymers (named ICPs for intrinsically conducting polymers, or ECPs for electroactive conducting polymers) were discovered in the seventies by McDiarmid, Heeger, and Shirakawa [1] who showed that unsaturated conjugated polymers (polyacetylene, polyphenylene) became conductive when doped, corresponding to the chemical oxidation of the ethylene or polyphenyl carbon chain. 

Composite matrix resin Conjugated and other unsaturated polymers Polyacetylene Polyaniline... 

Conjugated polymers can now claim a considerable and uninterrupted degree of attraction over a period of several decades [1]. In the initial years, research into the synthesis of the first representatives of the new substance class of conjugated polymers (polyacetylene, poly(para-phenylene), poly(parfl-phenylenevinylene), polythiophene, polypyrrole, polyaniline) was important. The resulting polymers were characterized in most cases by their insolubility and infusibility, properties that considerably hindered their structural characterization and their processing. The majority of such compounds possessed no fully defined structure and the physical properties were influenced by structural defects. Moreover, it was often difficult to distinguish between neutral molecules and the "doped" species resulting firom oxidation or reduction. 

Kaiser, A.B., S.A. Rogers, and Y.W. ParL 2004. Charge transport in conducting polymers Polyacetylene nanofibers. Mol Cryst Liq Ctyst 415 269. 

It is a gas, which is kept in cylinders and used for soldering iron. This shows that the flame arising from the burning of acetylene is very, very hot. From acetylene, we make the polymer polyacetylene (it is now used in batteries for electric cars). Acetylene is adso an example of molecules containing triple C C bonds, which, as a group, are called alkynes. 

Until the mid-seventies electrical conduction had been observed only in inorganic polymers and molecular crystals. In 1977, however, a group of scientists led by Heeger, Shirakawa and MacDiarmid (2) reported that an organic polymer, polyacetylene, could be made conducting by the addition of... 

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