Radical Polymerization of Styrene Mediated by Dinitrones of Various Structures
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MERIZATION
Radical Polymerization of Styrene Mediated by Dinitrones of Various Structures E. V. Kolyakinaa, A. B. Alyevaa, E. V. Sazonovaa, E. A. Zakharycheva, and D. F. Grishina,* a
National Research Nizhny Novgorod State University, Nizhny Novgorod, 603950 Russia *e-mail: [email protected] Received February 18, 2020; revised March 5, 2020; accepted March 19, 2020
Abstract—The effect of conjugated dinitrones N,N-dimethylglyoxaldinitrone, N,N-di-tert-butylglyoxaldinitrone, and N,N-diphenylglyoxaldinitrone on the radical polymerization of styrene initiated by azobis(isobutyronitrile) is studied. It is found that, during the polymerization of styrene at temperatures below 90°C, chains terminate on the studied nitrones to generate high molecular weight nitroxide radicals. The regularities of polystyrene synthesis in the presence of conjugated nitrones at 130°C (the first reaction order with respect to the monomer over the entire conversion range, a linear increase in molecular weight with conversion, and postpolymerization) indicate that the polymerization of styrene can be implemented under reversible inhibition conditions in the high temperature regime. It is shown that the acceptance and specific features of styrene polymerization mediated by nitroxide radicals formed in situ are directly related to the initial structure of dinitrones. For example, the presence of conjugation between phenyl and nitronyl groups in diphenyl dinitrone leads to a decrease in its accepting ability, lowering the effectiveness of high molecular weight nitroxides as polymerization regulators in the high temperature mode. Using the methods of static and dynamic light scattering, the hydrodynamic sizes of macromolecules are estimated and the form factor Rg/Rh of a linear polymer and polymers synthesized with the participation of dinitrones is calculated. DOI: 10.1134/S1560090420040077
INTRODUCTION Controlled radical polymerization or polymerization in the living chain mode occupies one of the leading positions in the modern synthetic chemistry of polymers [1], since it significantly expands the possibilities of conventional radical polymerization in terms of the synthesis of narrowly dispersed homopolymers and copolymers with predetermined molecular weight characteristics and a well-defined topology [2]. There are three main branches of controlled radical polymerization: Stable Free-Radical Polymerization (SFRP), that is, polymerization with the participation of stable radicals, including nitroxide ones (this method is called Nitroxide-Mediated Radical Polymerization, NMP); Atom Transfer Radical Polymerization (ATRP); and Degenerative Transfer Processes (DTP), that is, polymerization with degenerate chain transfer [1, 2]. Among these methods, the synthesis of polymers with the participation of stable nitroxide radicals in the reversible inhibition mode is one of the most famous and well-studied [3–6]. The polymers obtained under reversible inhibition conditions, as a rule, do not need additional purification, except for traditional repr
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