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{{Short description|Form of addition polymerization initiated with anions}}
{{Quote box|width = 35%
|title = [[International Union of Pure and Applied Chemistry|IUPAC]] definition
|quote = '''anionic polymerization''': An ionic polymerization in which the kinetic-chain carriers are anions.
<ref name='Gold Book "anionic polymerization"'>{{cite web |title=anionic polymerization |url=https://goldbook.iupac.org/terms/view/A00361 |website=Gold Book |publisher=IUPAC |access-date=1 April 2024 |ref=Gold Book A00361 |doi=10.1351/goldbook.A00361}}</ref>
}}
In [[polymer chemistry]], '''
== History ==
[[File:ET-coupledStyrene.png|thumb|Product of the reductive coupling of styrene with lithium, 1,4-dilithio-1,4-diphenylbutane. In the original work, Szwarc studied the analogous disodium compound.<ref>{{cite book|chapter=Ionic Polymerization|author=Sebastian Koltzenburg|author2=Michael Maskos|author3=Oskar Nuyken|title=Polymer Chemistry|isbn=978-3-662-49279-6|publisher=Springer|date=2017-12-11}}</ref>]]
As early as 1936, [[Karl Ziegler]] proposed that anionic polymerization of styrene and butadiene by consecutive addition of monomer to an alkyl lithium initiator occurred without chain transfer or termination. Twenty years later, living polymerization was demonstrated by [[Michael Szwarc]] and coworkers.<ref>{{cite journal|title=Polymerization Initiated by Electron Transfer to Monomer. A New Method of Formation of Block Polymers|first1=M.|last1=Szwarc|first2=M.|last2= Levy|first3=R.|last3=Milkovich|journal=J. Am. Chem. Soc.|year=1956|volume=78|issue=11|pages=2656–2657
|doi=10.1021/ja01592a101}}</ref><ref>{{cite journal|author=M. Szwarc |year=1956|title="Living" polymers|journal=Nature|volume=178|issue=4543|page=1168|doi=10.1038/1781168a0|bibcode=1956Natur.178.1168S}}</ref> In one of the breakthrough events in the field of [[polymer science]], Szwarc elucidated that [[electron transfer]] occurred from [[radical anion]] [[sodium naphthalene]] to [[styrene]]. The results in the formation of an organosodium species, which rapidly added styrene to form a "two – ended living polymer." An important aspect of his work, Szwarc employed the [[aprotic solvent]] [[tetrahydrofuran]]. Being a [[physical chemist]], Szwarc elucidated the [[chemical kinetics|kinetics]] and the [[thermodynamics]] of the process in considerable detail. At the same time, he explored the structure property relationship of the various [[ion pair]]s and radical ions involved. This work provided the foundations for the synthesis of polymers with improved control over [[molecular weight]], molecular weight distribution, and the architecture.<ref>Smid, J. Historical Perspectives on Living Anionic Polymerization. ''J. Polym. Sci. Part A.''; '''2002''', ''40'', pp. 2101-2107. [https://archive.today/20121012113202/http://www3.interscience.wiley.com/journal/94515609/abstract DOI=10.1002/pola.10286]</ref>
The use of [[alkali metals]] to initiate polymerization of 1,3-[[diene]]s led to the discovery by [[Frederick W. Stavely|Stavely]] and co-workers at Firestone Tire and Rubber company of cis-1,4-[[polyisoprene]].<ref name=Odian>Odian, G. Ionic Chain Polymerization; In '' Principles of Polymerization''; Wiley-Interscience: Staten Island, New York, 2004, pp. 372-463.</ref> This sparked the development of commercial anionic polymerization processes that utilize alkyllithium
[[Roderic Quirk]] won the 2019 [[Charles Goodyear Medal]] in recognition of his contributions to anionic polymerization technology. He was introduced to the subject while working in a [[Phillips Petroleum]] lab with [[Henry Hsieh]].
== Monomer characteristics ==
Two broad classes of monomers are susceptible to anionic polymerization.<ref name="Quirk"/>
Vinyl monomers have the formula CH<sub>2</sub>=CHR, the most important are styrene (R = C<sub>6</sub>H<sub>5</sub>), butadiene (R = CH=CH<sub>2</sub>), and isoprene (R = C(Me)=CH<sub>2</sub>). A second major class of monomers are acrylate esters, such as [[acrylonitrile]], [[methacrylate]], [[cyanoacrylate]], and [[acrolein]]. Other vinyl monomers include [[vinylpyridine]], vinyl [[sulfone]], vinyl [[sulfoxide]], [[vinyl silane]]s.<ref name="Quirk"/>
[[File:Ex polar monomers.png|thumb|300px|right|Examples of polar monomers]]
[[File:Example Vinyl monomer.png|thumb|200px|right|Examples of vinyl monomers]]
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The most commercially useful of these initiators has been the [[alkyllithium]] initiators. They are primarily used for the polymerization of styrenes and dienes.<ref name="Quirk"/>
Monomers activated by strong electronegative groups may be initiated even by weak anionic or neutral nucleophiles (i.e. amines, phosphines). Most prominent example is the curing of cyanoacrylate, which constitutes the basis for [[superglue]]. Here, only traces of basic impurities are sufficient to induce an anionic addition polymerization or [[zwitterionic addition polymerization]], respectively.<ref>Pepper, D.C. Zwitterionic Chain Polymerizations of Cyanoacrylates. ''Macromolecular Symposia''; '''1992''',''60'', pp. 267-277. {{doi|10.1002/masy.19920600124}}</ref>
== Propagation ==
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==Additional reading==
*Cowie, J.; Arrighi, V. ''Polymers: Chemistry and Physics of Modern Materials''; CRC Press: Boca Raton, FL, 2008.
*{{cite journal|author=Hadjichristidis, N.|author2=Iatrou, H.|author3=Pitsikalis, P.|author4=Mays, J.|title=Macromolecular architectures by living and controlled/living polymerizations|journal=Prog. Polym. Sci.|year=2006|volume=31|issue=12|pages=1068–1132|doi=10.1016/j.progpolymsci.2006.07.002}}
*{{cite journal|author=Efstratiadis, V.|author2=Tselikas, Y.|author3=Hadjichristidis, N.|author4=Li, J.|author5=Yunan, W.|author6=Mays, J.|title=Synthesis and characterization of poly(methyl methacrylate) star polymers|journal=Polym Int.|year=1994|volume=4|issue=2|pages=171–179|doi=10.1002/pi.1994.210330208}}
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