CONTROLLED RADICAL POLYMERIZATION OF STYRENE IN THE PRESENCE OF NITRONYL NITROXIDES

Bulk radical polymerization of styrene in the presence of nitronyl nit roxides (2-(4-substituted )-4,4,5,5-tetramethyl-4,5-dihydroimidazolyl- 1-oxyl 3-oxide) was studied. All nitronyl nitroxides, like other nitro xyl radicals such as 2,2,6,6-tetramethylpiperidine 1-oxyl radical (TEM PO), act as reversible radical scavengers. The efficiency of controlli ng the polymerization is affected by the substituent at the 4'-positio n. The efficiency increases with electron donating strength of 4'-subs tituents, at least at the beginning of the reaction. However, the ther mal stability of nitronyl nitroxides decreases in the same order. Thus , TEMPO is more suitable than nitronyl nitroxides for controlled/''liv ing'' radical polymerization of styrene.