Radical Polymerization of Styrene Mediated by Dinitrones of Various Structures.

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 R_g/R_h of a linear polymer and polymers synthesized with the participation of dinitrones is calculated. [ABSTRACT FROM AUTHOR]