US EPA

5716228 

Journal Article 

Mechanisms of living polymerization of vinyl monomers 

Yakimansky, AV 

2005 

1 

Polymer Science Series C
ISSN: 1811-2382
EISSN: 1555-614X 

47 

7 

1-49 

Russian 

WOS:000232670800001 

http://://RSCI:9149065
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In recent years, synthetic polymer chemistry has developed rapidly owing to the wide use of living polymerization techniques. Living anionic polymerization was discovered by M. Szwarc in the 1950s for nonpolar vinyl monomers (butadiene and styrene) and subsequently extended to polar vinyl monomers (acrylonitrile, acrylates, methacrylates, etc.). Later on, methods of livingness, that is, suppression of chain termination and transfer, were elaborated for both cationic (Sawamoto, Kennedy, etc.) and radical polymerizations (Matyjaszewski, etc.). The general principle underlying these processes is that the livingness of active species may be increased by reducing their reactivity via reversible transformation into the so-called dormant state. Examples of these living processes are provided by cationic polymerization carried out in the presence of electron donors, radical polymerization conducted in the presence of stable counter radicals, atom transfer radical polymerization, and reversible addition-fragmentation chain transfer polymerization. This review examines the general principles and the state of the art in this area. Special attention is given to the kinetics and mechanisms of these processes in relation to optimization and control of molecular-mass characteristics of the resulting polymers. The reactivity of various types of active species (associates, contact and separated ion pairs, polarized ionic bonds, and free ions and radicals) is considered, and methods of rapid exchange between all active and dormant species necessary for controlling chain propagation are discussed. Copyright © 2005 by MAIK "Nauka/Interperiodica " (Russia).