Wikipedia:WikiProject Chemicals/Chembox validation/VerifiedDataSandbox and Polyacetylene: Difference between pages

{{Short description|Organic polymer made of the repeating unit [C2H2]}}

{{About|polymers with alternating double and single bonds|compounds with multiple triple bonds|polyyne}}

|Verifiedfields = changed

|verifiedrevid = 464209345

|IUPACName = Polyethyne

|OtherNames = Polyacetylene, PAc

|ImageFile1 = Trans-Polyacetylene.svg

|ImageCaption1 = [[Skeletal formula]] of ''trans''-polyacetylene

|ImageName1 = ''trans''-polyacetylene

|ImageSize1 = 185px

|ImageFile2 = Cis-Polyacetylene.svg

|ImageCaption2 = Skeletal formula of ''cis''-polyacetylene

|ImageName2 = ''cis''-polyacetylene

|ImageSize2 = 180px

|ImageFile3 = Cis-and-trans-polyacetylene-chains-symmetric-8-based-on-xtals-3D-bs-17.png

|ImageCaption3 = [[Ball-and-stick model]]s of the transoidal (top) and cisoidal (bottom) conformations of the ''trans'' isomer<ref>{{cite journal |first1=Giovanni |last1=Perego |first2=Gabriele |last2=Lugli |first3=Ugo |last3=Pedretti |first4=Marco |last4=Cesari |title=X-ray investigation on highly oriented polyacetylene, 1. Crystal structure of cis- and trans-polyacetylene |journal=[[Die Makromolekulare Chemie|Makromol. Chem.]] |year=1988 |volume=189 |issue=11 |pages=2657–2669 |doi=10.1002/macp.1988.021891113}}</ref>

|Section1 = {{Chembox Identifiers

|CASNo_Ref = {{cascite|changed|??}}

|CASNo = 25067-58-7

|ChemSpiderID_Ref = {{chemspidercite|changed|chemspider}}

|ChemSpiderID = none

|Section2 = {{Chembox Properties

|Formula = {{chem2|[C2H2]_{''n''} }}

|Solubility = insoluble}}

|Section7 = {{Chembox Hazards

|GHSPictograms = {{GHS flame}}

|HPhrases = {{H-phrases|}}

|PPhrases = {{P-phrases|}}

}}

|Section3 = {{Chembox Related

|OtherCompounds = [[Ethyne]] (monomer)

}}

}}

'''Polyacetylene''' ([[IUPAC]] name: '''polyethyne''') usually refers to an [[organic polymer]] with the [[repeating unit]] {{chem2|[C2H2]_{''n''} }}. The name refers to its conceptual construction from [[polymerization]] of [[acetylene]] to give a chain with repeating [[olefin]] groups. This compound is conceptually important, as the discovery of polyacetylene and its high [[Ionic conductivity (solid state)|conductivity]] upon [[doping (semiconductor)|doping]] helped to launch the field of organic [[conductive polymer]]s. The high electrical conductivity discovered by [[Hideki Shirakawa]], [[Alan Heeger]], and [[Alan MacDiarmid]] for this polymer led to intense interest in the use of organic compounds in [[microelectronics]] ([[organic semiconductor]]s). This discovery was recognized by the [[Nobel Prize in Chemistry]] in 2000.<ref>{{cite journal |doi=10.1103/RevModPhys.73.681 |title=Nobel Lecture: Semiconducting and metallic polymers: The fourth generation of polymeric materials |year=2001 |last1=Heeger |first1=Alan |journal=Reviews of Modern Physics |volume=73 |issue=3 |pages=681–700 |bibcode=2001RvMP...73..681H |doi-access=free}}</ref><ref name="Nobel Prize">{{cite web |url=https://www.nobelprize.org/prizes/chemistry/2000/summary/ |title=The Nobel Prize in Chemistry 2000}}</ref> Early work in the field of polyacetylene research was aimed at using doped polymers as easily processable and lightweight "plastic metals".<ref name=Grubbs/> Despite the promise of this polymer in the field of conductive polymers, many of its properties such as instability to air and difficulty with processing have led to avoidance in commercial applications.

Compounds called polyacetylenes also occur in nature, although in this context the term refers to [[polyyne]]s, compounds containing multiple acetylene groups ("poly" meaning ''many''), rather than to chains of [[olefin fiber|olefin]] groups ("poly" meaning ''polymerization of'').<ref>{{cite journal |doi=10.1016/j.plipres.2008.02.002 |volume=47 |title=Biosynthesis and function of polyacetylenes and allied natural products |year=2008 |journal=Progress in Lipid Research |pages=233–306 |last1=Minto |first1=Robert E. |issue=4 |pmid=18387369 |pmc=2515280}}.</ref>

==Structure==

{{multiple image

| align = left

| direction = vertical

| header = A segment of ''trans''-polyacetylene

| width = 200

| image1 = Trans-(CH)n.svg

| caption1 = Structural diagram

| image2 = Polyacetylene-3D-balls.png

| caption2 = Ball-and-stick model

}}

Polyacetylene consists of a long chain of [[carbon]] atoms with alternating single and [[double bond]]s between them, each with one [[hydrogen]] atom. The double bonds can have either [[cis–trans isomerism|''cis'' or ''trans'' geometry]]. The controlled synthesis of each [[isomer]] of the polymer, ''cis''-polyacetylene or ''trans''-polyacetylene, can be achieved by changing the temperature at which the reaction is conducted. The ''cis'' form of the polymer is thermodynamically less stable than the ''trans'' isomer. Despite the [[conjugated system|conjugated]] nature of the polyacetylene backbone, not all of the carbon–carbon bonds in the material are equal: a distinct single/double alternation exists.<ref name=Norden/> Each hydrogen atom can be replaced by a [[functional group]]. Substituted polyacetylenes tend to be more rigid than saturated polymers.<ref name=Grubbs/> Furthermore, placing different functional groups as substituents on the polymer backbone leads to a twisted [[conformational isomerism|conformation]] of the polymer chain to interrupt the conjugation.

==History==

One of the earliest reported acetylene polymers was named Cuprene. Its highly cross-linked nature led to no further studies in the field for quite some time.<ref name=Feast>{{cite journal |last=Feast |first=W.J. |author2=Tsibouklis, J. |author3=Pouwer, K.L. |author4=Groenendaal, L. |author5=Meijer, E.W. |title=Synthesis, processing and material properties of conjugated polymers |journal=Polymer |date=1996 |volume=37 |issue=22 |page=5017 |doi=10.1016/0032-3861(96)00439-9}}</ref> Linear polyacetylene was first prepared by [[Giulio Natta]] in 1958.<ref name=Saxman>{{cite journal |last=Saxon |first=A.M. |author2=Liepins, F. |author3=Aldissi, M. |title=Polyacetylene: Its Synthesis, Doping, and Structure |journal=Prog. Polym. Sci. |date=1985 |volume=11 |issue=1–2 |page=57 |doi=10.1016/0079-6700(85)90008-5}}</ref> The resulting polyacetylene was linear, of high molecular weight, displayed high crystallinity, and had a regular structure. X-ray diffraction studies demonstrated that the resulting polyacetylene was ''trans''-polyacetylene.<ref name=Saxman/> After this first reported synthesis, few chemists were interested in polyacetylene because the product of Natta's preparation was an insoluble, air sensitive, and infusible black powder.

The next major development of polyacetylene polymerization was made by [[Hideki Shirakawa]]’s group who were able to prepare silvery films of polyacetylene. They discovered that the polymerization of polyacetylene could be achieved at the surface of a concentrated solution of the catalyst system of [[triethylaluminium|Et₃Al]] and Ti(OBu)₄ in an inert solvent such as toluene.<ref name=Norden>{{cite web |last=Norden |first=B |author2=Krutmeijer, E. |title=The Nobel Prize in Chemistry, 2000: Conductive Polymers |url=https://www.nobelprize.org/nobel_prizes/chemistry/laureates/2000/advanced-chemistryprize2000.pdf}}</ref> In parallel with Shirakawa's studies, [[Alan Heeger]] and [[Alan MacDiarmid]] were studying the metallic properties of [[polythiazyl]] [(SN)_x], a related but inorganic polymer.<ref name=Hall>{{cite journal |last1=Hall |first1=N |title=Twenty-five years of conducting polymers |journal=Chem. Comm. |date=2003 |doi=10.1039/B210718J |pages=1–4 |last2=McDiarmid |first2=Alan |last3=Heeger |first3=Alan |issue=1 |pmid=12610942 |url=http://teaching.ust.hk/~chem328/ChemComm03-1.pdf |access-date=2014-03-14 |url-status=dead |archive-url=https://web.archive.org/web/20160304023630/http://teaching.ust.hk/~chem328/ChemComm03-1.pdf |archive-date=2016-03-04}}</ref> Polythiazyl caught Heeger's interest as a chain-like metallic material, and he collaborated with [[Alan MacDiarmid]] who had previous experience with this material. By the early 1970s, this polymer was known to be [[superconductive]] at low temperatures.<ref name=Hall/> Shirakawa, Heeger, and MacDiarmid collaborated on further development of polyacetylene.<ref name=Saxman/>

Upon [[doping (semiconductor)|doping]] polyacetylene with I₂, the conductivity increased seven orders of magnitude.<ref name=Norden/> Similar results were achieved using Cl₂ and Br₂. These materials exhibited the largest room temperature conductivity observed for a covalent organic polymer, and this seminal report was key in furthering the development of organic [[conductive polymers]].<ref name="Shirakawa">{{cite journal |last=Shirakawa |first=H. |author2=Louis, E.J. |author3=MacDiarmid, A.G. |author4=Chiang, C.K. |author5=Heeger, A.J. |title=Synthesis of Electrically Conducting Organic Polymers: Halogen Derivatives of Polyacetylene, (CH)_x |journal=Journal of the Chemical Society, Chemical Communications |issue=16 |date=1977 |pages=578–580 |doi=10.1039/C39770000578}}</ref> Further studies led to improved control of the ''cis''/''trans'' isomer ratio and demonstrated that ''cis''-polyacetylene doping led to higher [[Ionic conductivity (solid state)|conductivity]] than doping of ''trans''-polyacetylene.<ref name="Norden" /> Doping ''cis''-polyacetylene with AsF₅ further increased the conductivities, bringing them close to that of copper. Furthermore, it was found that heat treatment of the catalyst used for polymerization led to films with higher conductivities.<ref>{{cite journal |last=Shirakawa |first=Hideki |title=Synthesis and characterization of highly conducting polyacetylene |journal=Synthetic Metals |date=1995 |volume=69 |issue=1–3 |page=3 |doi=10.1016/0379-6779(94)02340-5}}</ref>

To account for such an increase in conductivity in polyacetylene, [[John Robert Schrieffer|J. R. Schrieffer]] and Heeger considered the existence of topologically protected [[Soliton|solitonic]] defects, their model is now known as the [[Su–Schrieffer–Heeger model]], which has served as model in other contexts to understand [[Topological insulator|topological insulators]].<ref>{{Cite journal |last1=Meier |first1=Eric J. |last2=An |first2=Fangzhao Alex |last3=Gadway |first3=Bryce |date=2016 |title=Observation of the topological soliton state in the Su–Schrieffer–Heeger model |journal=Nature Communications |language=en |volume=7 |issue=1 |pages=13986 |doi=10.1038/ncomms13986 |issn=2041-1723 |pmc=5196433 |pmid=28008924|arxiv=1607.02811 |bibcode=2016NatCo...713986M }}</ref>

==Synthesis==

===From acetylene===

[[File:Ziegler natta scheme for polyacetylene.png|thumb|left|Ziegler–Natta scheme]]

A variety of methods have been developed to synthesize polyacetylene, from pure acetylene and other monomers. One of the most common methods uses a [[Ziegler–Natta catalyst]], such as [[titanium isopropoxide|Ti(O''i''Pr)₄]]/[[triethylaluminium|Al(C₂H₅)₃]], with gaseous acetylene. This method allows control over the structure and properties of the final polymer by varying temperature and catalyst loading.<ref>{{cite journal |last=Feast |first=W. J. |author2=Tsibouklis, J. |author3=Pouwer, K. L. |author4=Groenendaal, L. |author5=Meijer, E. W. |title=Synthesis, processing and material properties of conjugated polymers |journal=Polymer |date=1996 |volume=37 |issue=22 |pages=5017–5047 |doi=10.1016/0032-3861(96)00439-9}}</ref> Mechanistic studies suggest that this polymerization involves metal insertion into the triple bond of the monomer.<ref>{{cite journal |last=Clarke |first=T. C. |author2=Yannoni, T. S. |author3=Katz, T. J. |title=Mechanism of Ziegler–Natta Polymerization of Acetylene: A Nutation NMR Study |journal=Journal of the American Chemical Society |date=1983 |volume=105 |issue=26 |pages=7787–7789 |doi=10.1021/ja00364a076}}</ref>

[[File:Insertion mechanism for polyacetylene.png|thumb|Insertion mechanism for polyacetylene]]

By varying the apparatus and catalyst loading, Shirakawa and coworkers were able to synthesize polyacetylene as thin films, rather than insoluble black powders. They obtained these films by coating the walls of a reaction flask under inert conditions with a solution of the Ziegler–Natta catalyst and adding gaseous acetylene resulting in immediate formation of a film.<ref name=Ito>{{cite journal |author1=Ito, T. |author2=Shirakawa, H. |author3=Ikeda, S. |title=Simultaneous Polymerization and Formation of Polyacetylene Film on the Surface of Concentrated Soluble Ziegler-Type Catalyst Solution |doi=10.1002/pola.1996.854 |journal=Journal of Polymer Science Part A |date=1974 |volume=12 |issue=13 |pages=11–20 |bibcode=1996JPoSA..34.2533I}}</ref> Enkelmann and coworkers further improved polyacetylene synthesis by changing the catalyst to a [[cobalt(II) nitrate|Co(NO₃)₂]]/[[sodium borohydride|NaBH₄]] system, which was stable to both oxygen and water.<ref name=Feast/>

Polyacetylene can also be produced by [[radiation]] polymerization of acetylene. [[Glow discharge|Glow-discharge]] radiation, [[gamma radiation]], and [[ultraviolet]] irradiation have been used. These methods avoid the use of catalysts and solvent, but require low temperatures to produce regular polymers. Gas-phase polymerization typically produces irregular cuprene, whereas liquid-phase polymerization, conducted at −78&nbsp;°C produces linear ''cis''-polyacetylene, and solid-phase polymerization, conducted at still lower temperature, produces ''trans''-polyacetylene.<ref name=Saxman/>

===Ring-opening metathesis polymerization===

Polyacetylene can be synthesized by [[ring-opening metathesis polymerisation]] (ROMP) from [[cyclooctatetraene]], a material easier to handle than the [[acetylene]] [[monomer]].<ref>{{cite journal |last=Klavetter |first=Floyd L. |author2=Grubbs, Robert H. |title=Polycyclooctatetraene (Polyacetylene): Synthesis and Properties |journal=Journal of the American Chemical Society |date=1988 |volume=110 |issue=23 |pages=7807–7813 |doi=10.1021/ja00231a036}}</ref> This synthetic route also provides a facile method for adding solubilizing groups to the polymer while maintaining the conjugation.<ref name=Grubbs>{{cite journal |last=Gorman |first=C. B. |author2=Ginsburg, E. J. |author3=Grubbs, R. H. |title=Soluble, Highly Conjugated Derivatives of Polyacetylene from the Ring-Opening Metathesis Polymerization of Monosubstituted Cyclooctratetraenes: Synthesis and the Relationship between Polymer Structure and Physical Properties |journal=Journal of the American Chemical Society |date=1993 |volume=115 |issue=4 |pages=1397–1409 |doi=10.1021/ja00057a024}}</ref> [[Robert Grubbs]] and coworkers synthesized a variety of polyacetylene derivatives with linear and branched [[alkyl]] chains. Polymers with linear groups such as ''n''-[[octyl]] had high conductivity but low solubility, while highly branched ''tert''-[[butyl]] groups increased solubility but decreased [[conjugated system|conjugation]] due to polymer twisting to avoid [[steric]] crowding. They obtained soluble and conductive polymers with ''sec''-butyl and neopentyl groups, because the [[methylene group|methylene]] (CH₂) unit directly connected to the polymer reduces steric crowding and prevents twisting.<ref name=Grubbs/>

[[File:Modified Grubbs.png|thumb|center|upright 2.5|Grubbs route to polyacetylene]]

===From precursor polymers===

[[File:PVC base polyacetylene.png|thumb|300px|Dehydrohalogenation route to polyacetylene]]

Polyacetylene can also be synthesized from precursor polymers. This method enables processing of the polymer before conversion to insoluble polyacetylene. Short, irregular segments of polyacetylene can be obtained by [[dehydrohalogenation]] of [[poly(vinyl chloride)]].<ref>{{cite web |title=Conducting Polymers |url=https://www.ch.ic.ac.uk/local/organic/tutorial/steinke/4yrPolyConduct2003.pdf |work=ch.ic.ac.uk}}</ref>

Thermal conversion of precursor polymers is a more effective method for synthesizing long polyacetylene chains. In the Durham-precursor route, polymers are prepared by ring-opening metathesis polymerization, and a subsequent heat-induced reverse [[Diels–Alder reaction]] yields the final polymer, as well as a volatile side product.<ref name=Feast/>

[[File:Durham precursor 3.png|thumb|upright=2.5|center|Durham precursor polymer route to polyacetylene]]

==Doping==

When polyacetylene films are exposed to vapors of electron-accepting compounds ([[p-type semiconductor|p-type]] [[dopant]]s), the [[electrical conductivity]] of the material increases by orders of magnitude over the undoped material.<ref name=Chiang>{{cite journal |last=Chiang |first=C.K. |author2=Gau, S.C. |author3=Fincher, C.R. |author4=Park, Y.W. |author5=MacDiarmid, A.G. |author6=Heeger, A.J. |title=Polyacetylene, (CH)_x: n-type and p-type doping and compensation |journal=Appl. Phys. Lett. |date=1978 |volume=33 |issue=1 |page=18 |doi=10.1063/1.90166 |bibcode=1978ApPhL..33...18C}}</ref><ref name=":0">{{cite journal |last1=MacDiarmid |first1=Alan Graham |last2=Mammone |first2=R. J. |last3=Kaner |first3=R. B. |last4=Porter |first4=Lord |last5=Pethig |first5=R. |last6=Heeger |first6=A. J. |last7=Rosseinsky |first7=D. R. |last8=Gillespie |first8=Ronald James |last9=Day |first9=Peter |date=1985-05-30 |title=The concept of 'doping' of conducting polymers: the role of reduction potentials |url=https://royalsocietypublishing.org/doi/10.1098/rsta.1985.0004 |journal=Philosophical Transactions of the Royal Society of London. Series A, Mathematical and Physical Sciences |volume=314 |issue=1528 |pages=3–15 |doi=10.1098/rsta.1985.0004 |bibcode=1985RSPTA.314....3M |s2cid=91941666}}</ref> [[p-type semiconductor|p-Type]] [[dopant]]s include Br₂, I₂, Cl₂, and AsF₅. These [[dopant]]s act by abstracting an [[electron]] from the polymer chain. The [[ionic conductivity (solid state)|conductivity]] of these polymers is believed to be a result of the creation of [[charge-transfer complex]]es between the polymer and [[halogen]].<ref name=Shirakawa/> [[Charge-transfer complex|Charge transfer]] occurs from the polymer to the acceptor compound; the polyacetylene chain acts as a [[cation]] and the acceptor as an [[anion]]. The "hole" on the polymer backbone is weakly associated with the anionic acceptor by [[Coulomb potential]].<ref name=Chiang/> Polyacetylene doped with ([[p-type semiconductor|p-type]]) [[dopants]] retain their high conductivity even after exposure to air for several days.<ref name=Saxman/>

Electron-donating ([[n-type semiconductor|n-type]]) [[dopant]]s can also be used to create conductive polyacetylene.<ref name=":0"/> n-Type [[dopant]]s for polyacetylene include lithium, sodium, and potassium.<ref name=Saxman/> As with [[p-type semiconductor|p-type]] dopants, [[charge-transfer complex]]es are created, where the polymer backbone is [[anionic]] and the donor is [[cationic]]. The increase in conductivity upon treatment with an [[n-type semiconductor|n-type]] [[dopant]] is not as significant as those achieved upon treatment with a [[p-type semiconductor|p-type]] dopant. Polyacetylene chains doped with [[n-type semiconductor|n-type]] [[dopants]] are extremely sensitive to air and moisture.<ref name=Saxman/>

Polyacetylene can also be doped electrochemically.<ref name=":0"/>

The conductivity of polyacetylene depends on structure and doping. Undoped ''trans''-polyacetylene films have a conductivity of 4.4×10⁻⁵ Ω⁻¹cm⁻¹, while ''cis''-polyacetylene has a lower conductivity of 1.7×10⁻⁹ Ω⁻¹cm⁻¹.<ref name=":0"/> Doping with bromine causes an increase in conductivity to 0.5 Ω⁻¹cm⁻¹, while a higher conductivity of 38 Ω⁻¹cm⁻¹ is obtained through doping with iodine.<ref name="Shirakawa"/> Doping of either ''cis''- or ''trans''-polyacetylene leads to an increase in their conductivities by at least six orders of magnitude. Doped ''cis''-polyacetylene films usually have conductivities two or three times greater than doped ''trans''-polyacetylene even though the parent film has lower conductivity.<ref name="McDiarmiad synthetic metals"/>

==Properties==

The structure of polyacetylene films have been examined by both [[infrared spectroscopy]]<ref name="Shirikawa IR">{{cite journal |author1=Shirakawa, H. S. |author2=Ito, T. S. |author3=Ikeda, S. |title=Infrared Spectroscopy of Poly(acetylene) |doi=10.1295/polymj.2.231 |journal=Polym. J. |date=1971 |volume=2 |issue=2 |pages=231–244 |doi-access=free}}</ref> and [[Raman spectroscopy]],<ref name="Shirakawa Raman">{{cite journal |author1=Shirakawa, H. S. |author2=Ito, T. S. |author3=Ikeda, S. |title=Raman Scattering and Electronic Spectra of Poly(acetylene) |journal=Polym. J. |date=1973 |volume=4 |issue=4 |pages=460–462 |doi=10.1295/polymj.4.460 |doi-access=free}}</ref> and found that the structure depends on synthetic conditions. When the synthesis is performed below −78&nbsp;°C, the ''cis'' form predominates, while above 150&nbsp;°C the ''[[cis-trans isomerism|trans]]'' form is favored. At room temperature, the polymerization yields a ratio of 60:40 ''cis'':''trans''.<ref name="McDiarmiad synthetic metals"/> Films containing the ''cis'' form appear coppery, while the ''[[cis-trans isomerism|trans]]'' form is silvery.<ref name="McDiarmiad synthetic metals"/> Films of ''cis''-polyacetylene are very flexible and can be readily stretched, while ''[[cis-trans isomerism|trans]]''-polyacetylene is much more brittle.

The synthesis and processing of polyacetylene films affects the properties. Increasing the catalyst ratio creates thicker films with a greater draw ratio, allowing them to be stretched further.<ref name=Saxman/> Lower catalyst loadings leads to the formation of dark red [[gel]]s, which can be converted to films by cutting and pressing between glass plates.<ref name="McDiarmiad synthetic metals">{{cite journal |last=MacDiarmid |first=A |author2=Heeger, A. |title=Organic Metals and Semiconductors: The Chemistry of Polyacetylene (CH_x) and its Derivatives |journal=Synthetic Metals |date=1979 |volume=1 |issue=101–118 |pages=101 |doi=10.1016/0379-6779(80)90002-8 |url=https://apps.dtic.mil/sti/pdfs/ADA087102.pdf |url-status=live |archive-url=https://web.archive.org/web/20170924002910/http://www.dtic.mil/get-tr-doc/pdf?AD=ADA087102 |archive-date=September 24, 2017}}</ref> A foam-like material can be obtained from the gel by displacing the [[solvent]] with [[benzene]], then freezing and subliming the benzene.<ref name=Saxman/> Polyacetylene has a bulk density of 0.4&nbsp;g/cm³, while density of the foam is significantly lower, at 0.02–0.04&nbsp;g/cm³.<ref name=Saxman/> The morphology consists of [[fibril]]s, with an average width of 200&nbsp;Å. These fibrils form an irregular, web-like network, with some [[cross-link]]ing between chains.<ref name=Saxman/> The insolubility of polyacetylene makes it difficult to characterize this material and to determine the extent of cross-linking in the material.

[[File:Oxidation of Polyacetylene.jpg|thumb|right|500px|Products of oxidation of polyacetylene]]

For applications, polyacetylenes suffer from many drawbacks. They are insoluble in solvents, making it essentially impossible to process the material. While both ''cis'' and ''trans''-polyacetylene show high thermal stability,<ref name="McDiarmiad synthetic metals"/> exposure to air causes a large decrease in the flexibility and conductivity.<ref name=Saxman/> When polyacetylene is exposed to air, oxidation of the backbone by O₂ occurs. [[Infrared spectroscopy]] shows formation of [[carbonyl]] groups, [[epoxide]]s, and [[peroxide]]s.<ref name=Saxman/><ref>{{cite journal |last=Will |first=F.G. |author2=D.W. McKee |title=Thermal Oxidation of Polyacetylene |journal=Journal of Polymer Science |date=1983 |volume=21 |issue=12 |pages=3479–3492 |doi=10.1002/pol.1983.170211210 |bibcode=1983JPoSA..21.3479W}}</ref> Coating with [[polyethylene]] or wax can slow the [[oxidation]] temporarily, while coating with glass increases stability indefinitely.<ref name=Saxman/>

==Applications==

Polyacetylene has no commercial applications, although the discovery of polyacetylene as a conductive organic polymer led to many developments in materials science. Conducting polymers are of interest for solution-processing for film-forming conductive polymers.<ref name=Norden/> Therefore, attention has shifted to other [[conductive polymer]]s for application purposes including [[polythiophene]] and [[polyaniline]]. [[Molecular electronics]] could also be a potential application of conductive polyacetylene.

==See also==

*[[Polyene]]

==References==

{{Reflist|colwidth=30em}}

==External links==

* [https://romano.physics.wisc.edu/winokur/handbook/node5.html Polyacetylene]

* [https://www.nobelprize.org/prizes/chemistry/2000/ceremony-speech/ The Nobel Prize in Chemistry 2000 presentation speech]

[[Category:Molecular electronics]]

[[Category:Organic polymers]]

[[Category:Organic semiconductors]]

[[Category:Polyenes]]