Polyacetylenes high mechanical

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]. 

K. Akagi, M. Suezaki, H. Shirakawa, H. Kyotani, M. Shimomura, Y. Tanabe, Synthesis of polyacetylene flhn with high density and high mechanical strength, Synth. Met., 28, 1-6 (1989). 

Several attempts to induce orientation by mechanical treatment have been reviewed 6). Trans-polyacetylene is not easily drawn but the m-rich material can be drawn to a draw ratio of above 3, with an increase in density to about 70% of the close-packed value. More recently Lugli et al. 377) reported a version of Shirakawa polyacetylene which can be drawn to a draw ratio of up to 8. The initial polymer is a m-rich material produced on a Ti-based catalyst of undisclosed composition and having an initial density of 0.9 g cm-3. On stretching, the density rises to 1.1 g cm-3 and optical and ir measurements show very high levels of dichroism. The (110) X-ray diffraction peak showed an azimuthal width of 11°. The unoriented material yields at 50 MPa while the oriented film breaks at a stress of 150 MPa. The oriented material, when iodine-doped, was 10 times as conductive (2000 S cm-1) as the unstretched film. By drawing polyacetylene as polymerized from solution in silicone oil, Basescu et al.15,16) were able to induce very high levels of orientation and a room temperature conductivity, after doping with iodine, of up to 1.5 x 10s S cm-1. 

The search for new organic metals and superconductors has attracted a great deal of attention in synthetic chemistry and material science since the discovery of high electrical conductivity in conjugated polymers such as polyacetylene [1], Lots of theoretical studies have been carried out in order to understand the mechanism of conductivity and superconductivity in the conjugated polymers and related... 

This review describes the synthesis and properties of polyacetylenes with substituents (substituted polyacetylenes) mainly on the basis of our recent studies At first, Sections 2 and 3 survey the synthesis of substituted polyacetylenes with group 6 (Mo, W) and group 5 (Nb, Ta) transition metal catalysts respectively, putting emphasis on new, high-molecular-weight polyacetylenes. Then, Section 4 refers to the behavior and mechanism of the polymerization by these catalysts. Further, Section 5 explains the alternating double-bond structure, unique properties, and new functions of substituted polyacetylenes. Finally, Section 6 provides detailed synthetic procedures for substituted polyacetylenes. 

This combination of high electrical conductivity and outstanding mechanical properties has been demonstrated for doped polyacetylene [3-6,28-30]. Unfortunately, since doped polyacetylene is not a stable material, the achievement of stable high performance conducting polymers remains an important goal. 

The high level of interest in potential applications of polyacetylene (1), (CH)X, is tempered in many instances by the prospects of intractability and poor physical and mechanical properties. In an attempt to mitigate such undesirable characteristics, we have attempted to prepare copolymers and blends (or composites) in which the electroactive component is (CH)X. 

As described in Section II.B.l above, doping causes a drastic change in the electrical properties of polyacetylene. The initial values of electrical conductivity were of the order of 10 S cm" for unoriented materials d24-i30 when doped by iodine and AsFs, were enhanced to the order of 10 S cm, which was obtained in the parallel direction of the doped films oriented by mechanical stretching 31 Improvements in polymerization methods and in the catalyst systems also enhanced the electrical conductivity. Highly oriented films prepared in liquid crystal solvents (Section II.A.l.d.iii) exhibited a conductivity higher than 10 S cm, as did also a well stretch-oriented film prepared by Ti(OBu)4-EtsAl dissolved in silicon oil and aged at 120°C. In further studies Naarmann and Theophilou and Tsukamoto and coworkers attained a conductivity of ca 10 S cm k... 

In their evaluation of the high-pressure, solid-state polymerization at room temperature, Aoki et al. [17] have found that both ci.r- and frans-polyacetylene are formed, as is the case for the catalytic systems. The crystal structure of solid acetylene as determined by Koski and Sandor [162] by neutron diffraction on C2D2 at liquid helium temperature, is the starting point for their discussion of the mechanism. 

In this chapter the second moment studies are mainly reviewed for the two typical conjugated polymers Shirakawa-type (S-PA) [20-22,27,30-32] and Naar-mann and Theophilou-type (NT-PA) polyacetylenes [24] and polyparaphenylene [23,28,29]. The characteristic of NT-PA is a high degree of chain orientation attained by mechanical stretching, [33] which provides additional information on tlie polymer chain arrangement how much misorientatioii of the chains is left behind and how much of the amorphous portion exists [34]. From an analysis of the second moment M2... 

---