Acetylene polymerization Shirakawa method

Polyacetylene is most commonly obtained by the Shirakawa method in which acetylene gas is polymerized by using a Ziegler-Natta catalyst [10,11]. Many studies have been conducted on the chemical doping of polyacetylene [12-16]. It is also one of the most widely studied conductive polymers with respect to its electrochemical properties. 

Akagi, K., Sakamaki, K., and Shirakawa, H., Intrinsic nonsolvent polymerization method for synthesis of polyacetylene films, Synth. Med., 55, 779-784 (1993). Catellani, M., Destri, S., and Bolognesi, A., New catalytic systems for acetylene polymerization, MakromoL Chem., 187, 1345-1349 (1986). 

Four types of cis and tram structures are possible for PA (Fig. 1). Generally the trans-tramoid structure is simply termed tram, and the cis-tramoid structure is called cis. With the Shirakawa method either cis- or tram-YA can be synthesized. At a polymerization temperature of —78°C, ds-PA is formed exclusively. With increased temperature, a higher percentage of tram-PA forms (Ikble I). tram-PA forms exclusively at 150° C. At low temperatures a dr-structure arises predominantly from a cis insertion of the acetylene into the active site of the catalyst. Fukui and Inagaki suggest that a... 

Polyacetylenc is the simplest and most studied conductive polymer which can be produced by polymerization of acetylene or by thermal treatment of a precursor polymer. Although its red sensitivity due to its band gap of 1.5 eV is ideal for photo-voltaic applications, many workers have to shift their interest to other systems, due to its instability. However, with all its drawbacks and with the development of newer and newer methods of stabilization of conductive polymers, it is still fascinating many researchers due to its useful electrical and electronic applications [4,66-68]. Studies of the oxidation of Shirakawa polyacetylene have been reviewed by Chien [10] and Pochan [52]. 

For example, Shirakawa and co-workers [53] used three methods for the synthesis of PA films (1) polymerization of acetylene was carried out in a quiescent nematic solution in which the Ti(OBu)4 AlEt3 catalyst is dissolved homogeneously ... 

As is well known, polyacetylene can be manufactured by various processes using dilTerent catalysts. The most common method is that of Shirakawa [16,17], in which polymerization of acetylene takes place on a Ziegler catalyst. It has been shown in a large number of polymerization tests that the quality of the catalyst depends strongly on the preparation conditions [11]. 

A suspension of poly(acetylene) was prepared carrying out the polymerization as described by either Luttinger s or Shirakawa s method under rapid stirring of the catalyst solution into which acetylene was introduced by a gas inlet. 

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