Ziegler-Natta catalysts polyacetylene synthesis

Polyacetylene (PA), the simplest linear conjugated polymer, has been actively studied for two main reasons. First, the discovery of the direct synthesis method of PA films on the surface of a Ziegler-Natta catalyst solution [1]. Second, the discovery of a large increase in electronic conductivity, due to a synthetic metal by doping with small quantities of electron-attracting species such as iodine, AsFs, etc., or with an electron donor such as sodium. However, because of its high reactivity and poor solubility, it is difficult to obtain the experimental structural data of PA. 

The synthesis of the polyacetylene powder has been known since the late 1950s, when Natta used transition metal derivatives that have since become known as Ziegler-Natta catalysts. The characterization of this powder was difficult until Shirakawa and coworkers [18] succeeded in synthesizing lustrous, silvery, polycrystalline films of polyacetylene (which has become known as Shirakawa polyacetylene) and in developing techniques for controlling the content of cis and trans isomers ... 

Conducting polymers can be synthesized by following conventional polymer synthesis routes. One can transfer the Ziegler-Natta synthesis of polyethylene to polyacetylene. The Ziegler-Natta catalyst is solved in large excess in an inert solvent with acetylene streaming over the surface. A black film of polyacetylene is formed on the liquid surface. 

Among Ziegler-Natta catalysts derived from the transition metals of groups 4-8 in combination with organometallic compounds of groups 1-3, soluble catalysts used for polyacetylene synthesis are listed in Table 7.2. 

Electrochemical synthesis of polyacetylene was carried out with platinum foil as cathode and nickel foil as anode with nickel bromide in acetonitrile as an electrolyte at room temperature to precipitate in the form of powder in the cell [101]. Chen and Shy [53] observed a thin layer of black material on a surface of the platinum cathode when a voltage of 4-40 V was applied for about 50 min. During this stage, no precipitation of polyacetylene was observed in the solution. The material has the same chemical structure as those produced by the standard Ziegler-Natta catalyst as examined by elemental analysis, infrared spectroscopy. X-ray diffraction, and differential scanning calorimetry. 

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