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In polymer chemistry, living polymerization is a form of chain growth polymerization where the ability of a growing polymer chain to terminate has been removed.〔Moad, Graeme and Solomon, David H. (2006) ''The Chemistry of Radical Polymerization''. 2nd ed. Elsevier. ISBN 0-08-044286-2〕 This can be accomplished in a variety of ways. Chain termination and chain transfer reactions are absent and the rate of chain initiation is also much larger than the rate of chain propagation. The result is that the polymer chains grow at a more constant rate than seen in traditional chain polymerization and their lengths remain very similar (i.e. they have a very low polydispersity index). Living polymerization is a popular method for synthesizing block copolymers since the polymer can be synthesized in stages, each stage containing a different monomer. Additional advantages are predetermined molar mass and control over end-groups. Living polymerization is desirable because it offers precision and control in macromolecular synthesis. This is important since many of the novel/useful properties of polymers result from their microstructure and molecular weight. Since molecular weight and dispersity are less controlled in non-living polymerizations, this method is more desirable for materials design〔〔 In many cases, living polymerization reactions are confused or thought to be synonymous with controlled polymerizations. While these polymerization reactions are very similar, there is a distinct difference in the definitions of these two reactions. While living polymerizations are defined as polymerization reactions where termination or chain transfer is eliminated, controlled polymerization reactions are reactions where termination is suppressed, but not eliminated, through the introduction of a dormant state of the polymer.〔〔 However, this distinction is still up for debate in the literature. The main living polymerization techniques are: * Living anionic polymerization * Living cationic polymerization * Living ring-opening metathesis polymerization * Living free radical polymerization * Living chain-growth polycondensations ==History== Living polymerization was demonstrated by Michael Szwarc in 1956 in the anionic polymerization of styrene with an alkali metal / naphthalene system in tetrahydrofuran (THF) (see figure in "Living anionic polymerizations" section below). After initial addition of monomer to the initiator system, the viscosity would increase (due to increased polymer chain growth), but eventually cease after depletion of monomer concentration. However, he found that addition of ''more'' monomer caused an increase in viscosity, indicating growth of the polymer chain, and thus concluded that the polymer chains had never been terminated. This was a major step in polymer chemistry, since control over when the polymer was quenched, or terminated, was generally not a controlled step. With this discovery, the list of potential applications expanded dramatically. Today, living polymerizations are used widely in the development of various types of polymers or plastics. This is because chemists now have easy control of the chemical makeup of the polymer and, thus, the structural and electronic properties of the material. This level of control rarely exists in non-living polymerization reactions, leaving this method as the preferred synthetic route if attainable.〔〔 The most common types of living polymerization reactions are anionic, cationic, free-radical, or ring-opening in nature, the specifics of each are discussed in the techniques section. In addition, while copolymers are possible to create using non-living polymerization reactions, the types of copolymers and the precise control of the chemical structure was expanded through the discovery of living polymerizations.〔 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Living polymerization」の詳細全文を読む スポンサード リンク
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