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'''Anionic addition polymerization''' is a form of [[chain-growth polymerization]] or [[addition polymerization]] that involves the [[polymerization]] of vinyl monomers initiated with stronganions. The type of reaction has many manifestations, electronegativebut groupstraditionally vinyl monomers are used.<ref name=Hsieh>Hsieh, H.;Quirk, R. ''Anionic Polymerization: Principles and practical applications''; Marcel Dekker, Inc: New York, 1996.</ref><ref name=Quirk>Quirk, R. Anionic Polymerization. In ''Encyclopedia of Polymer Science and Technology''; John Wiley and Sons: New York, 2003.</ref> This polymerizationOften isanionic carriedpolymerization out through ainvolves [[carbanion]] active species.<ref>Blackeley, D.; Twaits, R. Ionic Polymerization. In ''Addition Polymers: Formation and Characterization''; Plenum Press: New York, 1968; pp. 51-110.</ref> Like all chain-growth polymerizations, it takes place in three steps: [[chain initiation]], [[chain propagation]], and [[chain termination]]. [[Livingliving polymerization]]s, which lack a formal termination pathway, occur in many anionic addition polymerizations. The advantage of living anionic addition polymerizations is that they allow for theallows control of structure and composition.<ref name="Hsieh"/><ref name="Quirk"/>
Anionic polymerizations are used in the production of polydiene [[synthetic rubber]]s, solution styrene/butadiene rubbers (SBR), and styrenic [[thermoplastic elastomers]].<ref name="Hsieh"/>
In anionic polymerizations, the end group of growing macro molecule possess high activity and good stability. Polymerization process continues till the available monomers are consumed.
== History ==
== Propagation ==
[[File:RLi+Styrene.png|center|640px|thumb|Organolithium-initiated polymerization of styrene.]]
Propagation in anionic addition polymerization results in the complete consumption of monomer. ItThis stage is veryoften fast, and occurseven at low temperatures. This is due to the anion not being very stable, the speed of the reaction as well as that heat is released during the reaction. The stability can be greatly enhanced by reducing the temperatures to near 0˚C. The propagation rates are generally fairly high compared to the decay reaction, so the overall polymerization rates is generally not affected.<ref name="Hsieh"/>
==Living anionic polymerization==
Chain transfer can occur when an agent can act as a [[Acid#Brønsted-Lowry acids|Brønsted acid]]. In this case, the [[pKa]] value of the agent is similar to the conjugate acid of the propagating carbanionic chain end. Spontaneous termination occurs because the concentration of carbanion centers decay over time and eventually results in hydride elimination.<ref name=Odian/>
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==Additional reading==
*Cowie, J.; Arrighi,V. ''Polymers: Chemistry and Physics of Modern Materials''; CRC Press: Boca Raton, FL, 2008.
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