Anionic addition polymerization: Difference between revisions

Revision as of 15:33, 16 July 2021

Revision as of 05:13, 16 October 2021

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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. [http://onlinelibrary.wiley.com/{{doi/|10.1002/masy.19920600124/abstract}}</ref>

== Propagation ==

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Synthesis of block copolymers is one of the most important applications of living polymerization as it offers the best control over structure. The [[nucleophilicity]] of the resulting carbanion will govern the order of monomer addition, as the monomer forming the less nucleophilic propagating species may inhibit the addition of the more nucleophilic monomer onto the chain. An extension of the above concept is the formation of triblock copolymers where each step of such a sequence aims to prepare a block segment with predictable, known molecular weight and narrow molecular weight distribution without chain termination or transfer.<ref>Hsieh, H.;Quirk, R. Anionic Polymerization: Principles and practical applications; Marcel Dekker, Inc.: New York, 1996.</ref>

Sequential monomer addition is the dominant method, also this simple approach suffers some limitations.</ref>

Moreover, this strategy, enables synthesis of linear block copolymer structures that are not accessible via sequential monomer addition. For common A-b-B structures, sequential block copolymerization gives access to well defined

block copolymers only if the crossover reaction rate constant is significantly higher than the rate constant of the homopolymerization