Polyacetylene 733183 213262978 2008-05-18T15:50:25Z Tendermecies 7028118 /* Preparation */ '''Polyacetylene''' ([[IUPAC]] name: polyethyne) is an [[organic polymer]] with the repeat unit (C<sub>2</sub>H<sub>2</sub>)<sub>n</sub>. The high electrical conductivity discovered for these polymers in the 1970’s accelerated interest in the use of [[organic compound]]s in [[microelectronics]]. Polyacetylenes are also known where the H atoms are replaced with [[alkyl]] groups. ==Structure of polyacetylene== The polymer consists of a long chain of [[carbon]] atoms with alternating single and [[double bond]]s between them, each with one [[hydrogen]] atom. Schematically the structure of polyacetylene is shown below. [[Image:Trans-(CH)n.png|400px||thumb|center|A segment of ''trans''-polyacetylene.]] One distinguishes ''trans-polyacetylene'', with all double bonds in the [[trans]] configuration, from ''cis-polyactylene'', with all double bonds in the [[cis]] configuration. Each hydrogen atom could be replaced by a [[functional group]]. ==Preparation== Acetylene polymerizes in a similar fashion to [[ethylene]]: the [[polymerization]] can be effected with anionic, cationic, and radical [[initiator]]s. Polyacetylene is generally not prepared by polymerizing [[acetylene]], which is a highly flammable gas that uncontrollably [[oligomer]]izes at high concentrations. The most common syntheses use [[olefin metathesis|ring-opening]] polymerization ("ROMP") of molecules like [[cyclooctatetraene]] and substituted derivatives thereof.<ref>Jozefiak, T. H.; Ginsburg, E. J.; Gorman, C. B.; Grubbs, R. H.; Lewis, N. S."Voltammetric Characterization of Soluble Polyacetylene Derivatives Obtained from the Ring-Opening Metathesis Polymerization (ROMP) of Substituted Cyclooctatetraenes" Journal of the American Chemical Society 1993; volume 115, pages 4705-4713. {{DOI|10.1021/ja00064a035}}</ref><ref>Gorman, C. B. Ginsburg, E. J.; [[Robert H. Grubbs|Grubbs]], R. H. "Soluble, Highly Conjugated Derivatives of Polyacetylene from the Ring-Opening Metathesis Polymerization of Monosubstituted Cyclooctatetraenes: Synthesis and the Relationship Between Polymer Structure and Physical Properties" Journal of the American Chemical Society 1993, volume 115, pages 1397-1409. {{DOI|10.1021/ja00057a024}}</ref><ref>Langsdorf, Brandi, L.; Zhou, Xin; Lonergan, Mark C., "Kinetic Study of the Ring-Opening Metathesis Polymerization of Ionically Functionalized Cyclooctatetraenes" Macromolecules, 2001, volume 34, pages 2450-2458. {{DOI|10.1021/ma0020685}}</ref> ==Conductivity and the Nobel Prize== As prepared with a [[Ziegler-Natta catalyst]], with high levels of [[catalyst]], the polyacetylene is a silver, non-conductive film. It was shown in 1976 that oxidation of this material with [[iodine]] results in a 10<sup>8</sup>-fold increase in conductivity. The conductivity of this doped material approaches the conductivity of the best available conductor, [[silver]]. This was one of the first known examples of a conductive organic polymer.<ref>Chiang, C. K.; Druy, M. A.; Gau, S. C.; Heeger, A. J.; Louis, E. J.; MacDiarmid, A. G.; Park, Y. W.; Shirakawa, H., "Synthesis of Highly Conducting Films of Derivatives of Polyacetylene, (CH)x," J. Am. Chem. Soc. 1978, 100, 1013-15. {{DOI|10.1021/ja00471a081}}</ref> The [[Nobel Prize in Chemistry]] in 2000 was awarded to [[Alan J. Heeger]], [[Alan G MacDiarmid]], and [[Hideki Shirakawa]] for this work. ==References== <references/> ==External links== * [http://romano.physics.wisc.edu/winokur/handbook/node5.html Polyacetylene] * [http://nobelprize.org/chemistry/laureates/2000/presentation-speech.html The Nobel Prize in Chemistry 2000 presentation speech] [[Category:Organic polymers]] [[Category:Molecular electronics]] [[Category:Organic semiconductors]] [[de:Polyethin]] [[fr:Polyacétylène]] [[it:Poliacetilene]] [[ja:ポリアセチレン]] [[pl:Poliacetylen]] [[sr:Полиацетилен]]