Polyacetylene
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Polyacetylene (PA) is an organic polymer and organic semiconductor prepared either synthetically or as one form of the biological pigment melanin. Some fungal melanins are pure polyacetylene.
Polyacetylene can be converted to a conducting polymer of the rigid-rod polymer host family. As prepared by a Ziegler-Natta catalyst, with high levels of catalyst, the polymer is a silver, non-conductive film. Oxidation with iodine provides a 108 increase in conductivity. The 2000 Nobel Prize in Chemistry was awarded to Alan J. Heeger, Alan G MacDiarmid, and Hideki Shirakawa for this work.
However, in 1963, Weiss et al had reported [1][2] equivalent high-conductivity in similarly iodine-doped polypyrrole, a polyacetylene derivative. Further, John McGinness, Peter Corry, and Peter Proctor had reported a working active organic electronics device using melanin, also highly-oxidized. This voltage-controlled solid state switch demonstrated similar high conductivity in the ON state.
The polymerization of the acetylene (chemical formula C2H2, structurally: HC≡CH) results in a long chain of carbon atoms with alternating single and double bonds between them, each with one hydrogen atom which could be replaced by a functional group. Schematically (with hydrogen atoms not shown) ...C=C-C=C-C...
Polyacetylene, prepared differently, is also called acetylene black, polyacetylene black or melanin.
