Polyacetylenes, produced

Polymer Batteries The discovery that doping of polyacetylene produced a highly conducting material was followed swiftly by the realization that this material was a rechargeable battery material which, optimistically, might lead to lightweight... 

FIGURE 6.5 The band gap in polyacetylene produced by the alternation of long and short bonds. 

The aromatic residue may be any of a large number of such units but the favourite for academic study has been the perfluoromethylxylene derivative shown, which smoothly eliminates at around room temperature to give a polyacetylene containing 25 % of trans- and 75 % of m-units. After transformation and isomerization at 80 °C, the polyacetylene produced is a continuous dense film. The physical chemistry of the transformation and isomerization reactions has been studied in detail229,230) and the properties of the polyacetylene are reviewed 231). The great advantage of this route is that the precursor is a soluble polymer so that it can be characterized and the physical form of the polyacetylene can be controlled. 

The same authors 369,3701 also obtained similar results if the liquid crystal solvent was aligned by flow during the polymerization. They showed that the polymerization conditions lead to alignment of the fibrils within the polymer mass and of the chains within the fibrils polymers produced in this way could also be doped to a conductivity of 104 S cm-1 371). The morphology of polyacetylene produced by polymerization in a liquid crystal solvent, aligned both magnetically and by flow, has been studied by Montaner et al. 371). They show that the polymer film is made up of very long fibrils built from microfibrils. In one fibril, the orientation of microcrystalline domains with respect to the fibril axis is very well defined, whilst the orientation of the different fibrils in the sample spreads over 20°. 

In our own studies of the isomerisation of the 75% e/s-polyacetylene produced by the Durham route 347> we have been unable to detect any effect on the isomerisation process of illumination with modest levels of light. We do find that the isomerisation is markedly affected by even trace amounts of oxygen, which lead to a change in the apparent order of reaction and a marked lowering of activation energy, somewhat similar to the observations of Chien and Yang 447) for conventional polymer. However, polymers prepared by the Durham route are very different from Shirakawa polymer and it would be unwise to extrapolate our results to Shirakawa materials. 

When well-defined, less Lewis-acidic metathesis polymerization catalysts are used to polymerize COT, a lower level of detectable sp defects are formed. Also, although the polyacetylene produced is still insoluble, the reaction proceeds slowly enough to allow manipulation of the liquid reaction solution before hardening. In this way, one can obtain films in a desired shape and location, e.g., on a semiconductor [123]. This procedure was found to result in better electrical contact than can be obtained when a free-standing film prepared via the Shirakawa route is simply pressed against an electrode. 

Note that from the answer to part (b), aU the atoms in acetylene go into polyacetylene. Due to conservation of mass, then, the mass of polyacetylene produced must also be 5.32 g, if we assmne 100% yield. 

Equation (15-17) tells us how to produce wavefunctions. We simply take exp(/fa) times our basis set, with k taking on all values between —nja and n ja, and pick off values at discrete points corresponding to carbon atom positions. Since it is more convenient to work with the real forms of solutions, we in effect choose a pair of k values (e.g., —7r/4a and 7r/4a) so that we can generate a pair of trigonometric coefficient waves [cos(7Tx/4a) and sin(7rx/4a)]. Thejr MOs for regular polyacetylene produced from Bloch sums are shown in Fig. 15-8 for selected values of k. These can be used to illustrate some important points ... 

Klavetter and Grubbs [65] developed a versatile and convenient route to polyacetylene through the condensed-phase polymerization of the monomer with the well-defined metathesis tungsten-based catalysts 10 and 11, as shown in Fig. 7.7. Shiny and silvery films with a smooth surface were prepared by dissolution of catalyst 10 in 50-150 equivalents of COT and subsequent polymerization on a glass surface at ambient temperature and pressure. Properties of these poly-COT films are nearly identical with those of polyacetylene produced with Ziegler-Natta catalysts. 

For a long time there was no consensus of opinion about the morphology of ICPs. On the basis of scanning electron micrographs, some research groups favored a fibrillar structure for PAc (polyacetylene) produced by the Shirakawa method [15]. This would, it was thought, be an explanation for an anisotropy of electrical conductivity that was observed following orientation of the material [26]. 

Silverman, W. B., and M. Anchel Similar polyacetylenes produced by species of Clitocyhe and related genera. Federation Proc. 18, 324 (1959). 

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