RADICAL POLYMERIZATIONS OF METHYL-METHACRYLATE INITIATED BY METHYL ETHYLENE)-2,5-CYCLOHEXADIENYL]-2-METHYL-PROPANOATE - A MODEL SYSTEM FOR SO-CALLED QUASI-LIVING POLYMERIZATIONS OF METHYL-METHACRYLATE INITIATED BY PHENYLAZOTRIPHENYLMETHANE

The kinetics of radical polymerizations of methyl methacrylate initiat ed by methyl thylene)-2,5-cyclohexadienyl]-2-methyl-propanoate, a mode l for the growing chain end in 'quasi-living' radical polymerizations of methyl methacrylate mediated by trityl radicals, conventionally gen erated from phenylazotriphenylmethane, have been investigated. It is s hown that the polymerizations have many of the characteristics of livi ng systems, including the ability for polymer chains recovered from th e polymerizations to reinitiate polymerization when added to fresh mon omer. However, molecular weight distributions of polymers broaden cons iderably with conversion, suggesting significant termination, probably via transfer to trityl radicals and/or conventional bimolecular termi nation. Also, the polymers recovered from reinitiation experiments hav e molecular weights which are too high to be consistent with simple re initiation via regeneration of growing radicals; rather it seems proba ble that reinitiation occurs via breakdown of a peroxidic species intr oduced during work-up of the original polymer. (C) 1998 Elsevier Scien ce Ltd. All rights reserved.