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Ionic and covalent species in the cationic polymerization – equilibria and reactivities

✍ Scribed by K. Matyjaszewski; R. Szymański; P. Kubisa; St. Penczek

Publisher
John Wiley and Sons
Year
1984
Tongue
English
Weight
874 KB
Volume
35
Category
Article
ISSN
0323-7648

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✦ Synopsis

Structure and reactivities in the cationic polymerization of the heterocyclic monomers is reviewed. Particularly the equilibria between major kinds of active species, including the kinetics of interconversions between the covalent species and the corresponding macroion-pairs are discussed. Reason for the higher reactivity of the ionic species than of the covalent ones in the chain growth, observed in the majority of studied systems, is confronted with the recently observed similarity in reactivities, found for oxepane. Further evidence is discussed, supporting the earlier formulated opinion that ion-pairs and ions propagate with similar rate constants. These features of the cationic ring-opening polymerizations were compared with the cationic vinyl polymerization. In the former process the covalent and ionic active species have separately been observed by NMR and the covalent propagation clearly demonstrated, whereas there is only a secondary and weak support for the covalent growth of vinyl monomers.

Ionische und covalente Zentren bei der kationischen Polymerisation. Gleichgewichte und Reaktivitaten

Ein Uberblick uber die Bedeutung der Struktur und Reaktivitat von heterocyclischen Monomeren bei derkationischen Polymerisation wird gegeben. Besonders die Gleichgewichte zwischen den wichtigsten Arten aktiver Zentren werden unter Berucksichtigung der Reaktionskinetik zwischen covalenten Zentren und entsprechenden Makroionenpaaren diskutiert. Die im Vergleich zu den covalenten Zentren hohere Reaktivitat der ionischen Zentren beim Kettenwachstum, die bei den meisten untersuchten Systemen beobachtet wurde, wird der kurzlich beobachteten Ahnlichkeit der Reaktivitat, wie sie fur Oxepan festgestellt wurde, gegenubergestellt. Weitere Beweise fur die fruher geauI3erte Vorstellung

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