Imidazolidinone nitroxide-mediated polymerization

Derivatives of 2,2,5,5-tetraalkylimidazolidin-4-one-1-oxyl have been found to offer significant advantages over many of the nitroxides previously empl oyed in nitroxide-mediated polymerization: homopolymers [e.g., polystyrene and poly(alkyl acrylate)], statistical copolymers [e.g., poly(styrene-co-ac rylonitrile)], and block copolymers [e.g., poly(4-methylstyrene)-block-poly styrene and poly(n-butyl acrylate)-block-polystyrene] can be synthesized wi th controlled molecular weight, narrow molecular weight distribution, and d efined end group functionality. The effect of substituents a to the nitroxi de nitrogen and at the transannular nitrogen on the outcome of polymerizati on is explored. Appropriate selection of these substituents provides polyme rs of lower polydispersities than, for example, 2,2,6,6-tetramethylpiperidi n-2-oxyl and derivatives. The nitroxides are synthesized from readily avail able precursors by a simple experimental route. Moreover, they are subject to fewer side reactions. In particular, disproportionation between the prop agating radical with nitroxide appears to be of lesser significance.