Polyacetylene

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This article is about polymers with alternating double and single bonds. For compounds with multiple triple bonds, see polyyne.
Polyacetylene
IUPAC name

Polyethyne

Other names

Polyacetylene, PAc

Identifiers
CAS number 25067-58-7 N
Properties
Molecular formula [C2H2]n
Solubility in water insoluble
Hazards
R-phrases R10
S-phrases –
Related compounds
Related compounds Ethyne (monomer)
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Except where noted otherwise, data are given for materials in their standard state (at 25 °C (77 °F), 100 kPa)
Infobox references

Polyacetylene (IUPAC name: polyethyne) is an organic polymer with the repeating unit (C2H2)n. The high electrical conductivity discovered for these polymers led to intense interest in the use of organic compounds in microelectronics (organic semiconductors). The discovery of the high conductivity of polyacetylene by Hideki Shirakawa, Alan J. Heeger, and Alan G MacDiarmid was recognized by the Nobel Prize in Chemistry in 2000.[1]

Structure of polyacetylene

The polymer consists of a long chain of carbon atoms with alternating single and double bonds between them, each with one hydrogen atom. Schematically the structure of polyacetylene is shown below.

A segment of trans-polyacetylene

Structural diagram
Ball-and-stick model

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 can be replaced by a functional group.

Preparation

Interest in the conductive properties of oxidatively doped polyacetylenes was ignited in the mid 1970s with the discovery of a silvery, conductive polyacetylene by Hideki Shirakawa. He polymerized acetylene with 1000 times the amount of catalyst normally used when performing the reaction. Shirakawa later collaborated with physicist Alan J. Heeger and chemist Alan G MacDiarmid, discovering in 1976 that oxidation of this material with iodine results in a 108-fold increase in conductivity. The conductivity of this doped material can approach the conductivity of the best available conductor, silver. The three were awarded the Nobel Prize in Chemistry in 2000 for their discoveries.[2][3]

Polyacetylene is generally not prepared by polymerizing acetylene because of the violence of its uncontrolled polymerization. The most common syntheses use ring opening metathesis polymerisation ("ROMP") of molecules like cyclooctatetraene[4][5] and substituted derivatives thereof.[6][7][8]

References

  1. ↑ Heeger, Alan (2001). "Nobel Lecture: Semiconducting and metallic polymers: The fourth generation of polymeric materials". Reviews of Modern Physics (free download) 73 (3): 681. doi:10.1103/RevModPhys.73.681. 
  2. ↑ Chiang, C. K.; Druy, M. A.; Gau, S. C.; Heeger, A. J.; Louis, E. J.; MacDiarmid, A. G.; Park, Y. W.; Shirakawa, H. (1978). "Synthesis of Highly Conducting Films of Derivatives of Polyacetylene, (CH)x". Journal of the American Chemical Society 100 (3): 1013. doi:10.1021/ja00471a081. 
  3. ↑ Ebbing, Darrell; Steven Gammon (2005). General Chemistry (8th ed.). New York: Houghton Mifflin Company. pp. 1042–1043. ISBN 0-618-399410. 
  4. ↑ Korshak Yu. V., Korshak V. V., Kanischka G., Hoeker H (1985). Die Makromolekulare Chemie, Rapid Communications 6 (10): 685. doi:10.1002/marc.1985.030061010. 
  5. ↑ V. V. Berdyugin, K. Ya. Burshtein, P. P. Shorygin, Yu. V. Korshak, A. V. Orlov, M. A. Tlenkopachev "Structure of Polyacetylene Obtained from Cyclooctatetraene" Proc. Acad. Sci. USSR, 1990, Phys. Chem. Sect. 312, 410 (English translation)
  6. ↑ Jozefiak, T. H.; Ginsburg, E. J.; Gorman, C. B.; Grubbs, R. H.; Lewis, N. S. (1993). "Voltammetric characterization of soluble polyacetylene derivatives obtained from the ring-opening metathesis polymerization (ROMP) of substituted cyclooctatetraenes". Journal of the American Chemical Society 115 (11): 4705. doi:10.1021/ja00064a035. 
  7. ↑ Gorman, C. B. Ginsburg, E. J.; Grubbs, R. H. (1993). "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 115 (4): 1397. doi:10.1021/ja00057a024. 
  8. ↑ Langsdorf, Brandi, L.; Zhou, Xin; Lonergan, Mark C. (2001). "Kinetic Study of the Ring-Opening Metathesis Polymerization of Ionically Functionalized Cyclooctatetraenes". Macromolecules 34 (8): 2450. doi:10.1021/ma0020685. 

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