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== Monomer characteristics ==
Two broad classes of monomers are susceptible to anion-induced polymerization.<ref name="Quirk"/>
===Vinyl monomers===
Vinyl monomers have the formula CH<sub>2</sub>=CHR, andthe most important are styrene (R = C<sub>6</sub>H<sub>5</sub>), butadiene (CH=CH<sub>2</sub>), and isoprene (R = C(RMe)=CH<sub>2</sub>)Z. SomeA ofsecond themajor mostclass importantof monomers are styreneacrylate esters, butadienesuch as [[acrylonitrile]], [[methacrylate]], [[cyanoacrylate]], and isoprene[[acrolein]]. ManyOther acrylatevinyl estersmonomers areinclude ammenable[[vinylpyridine]], vinyl [[sulfone]], vinyl [[sulfoxide]], [[vinyl silane]]s.<ref name="Quirk"/>
[[Image:Ex polar monomers.png|thumb|300px|center|Examples of polar monomers.]]
===Cyclic monomers===
Many cyclic compounds are susceptible to [[ring-opening polymerization]]. [[Epoxide]]s, cyclic tri[[trisiloxanesiloxane]]s, some lactones, [[lactide]]s, [[cyclic carbonate]]s, and [[amino acid N-carboxyanhydride]]s.
In order for polymerization to occur with [[vinyl group|vinyl]] [[monomer]]s, the [[substituent]]s on the [[double bond]] must be able to stabilize a [[negative charge]]. Stabilization occurs through [[delocalization]] of the negative charge. Because of the nature of the [[carbanion]] propagating center, substituents that react with bases or nucleophiles either must not be present or be protected.<ref name="Quirk"/>
[[Image:Example Vinyl monomer.png|thumb|200px|left|Examples of vinyl monomers.]]
[[Image:Example Vinyl monomer.png|thumb|200px|left|Examples of vinyl monomers.]]Vinyl monomers with substituents that stabilize the negative charge through charge delocalization, undergo polymerization without termination or chain transfer.<ref name="Quirk"/> These monomers include [[styrene]], [[diene]]s, [[methacrylate]], vinyl [[pyridine]], [[aldehyde]]s, [[epoxide]], [[episulfide]], cyclic [[siloxane]], and [[lactone]]s.
Polar monomers, using controlled conditions and low temperatures, can undergo anionic polymerization. However, at higher temperatures they do not produce living stable, carbanionic chain ends because their polar substituents can undergo side reactions with both initiators and propagating chain centers. The effects of counterion, solvent, temperature, Lewis base additives, and inorganic solvents have been investigated to increase the potential of anionic polymerizations of polar monomers.<ref name="Quirk"/> Polar monomers include [[acrylonitrile]], [[cyanoacrylate]], [[propylene oxide]], vinyl [[ketone]], [[acrolein]], vinyl [[sulfone]], vinyl [[sulfoxide]], [[vinyl silane]] and [[isocyanate]].[[Image:Ex polar monomers.png|thumb|300px|center|Examples of polar monomers.]]
== Initiation ==
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