INVESTIGATION OF METHYL-METHACRYLATE AND VINYL-ACETATE POLYMERIZATIONPROMOTED BY AL(BU-I)(3) 2,2'-BIPYRIDINE AND AL(BU-I)(3)/2,2'-BIPYRIDINE/TEMPO COMPLEXES/

Results of methyl methacrylate (MMA) and vinyl acetate (VOAc) polymeri zation using the Al(Bu-i)(3)/2,2'-bipyridine/TEMPO initiating system a t room temperature failed to confirm the ''living'' radical mechanism reported earlier. Several species apparently propagate without control in a normal free radical process and only above a critical initiator concentration. No evidence was found for the penta- and hexacoordinate d aluminum species previously suggested, but high conversion to an alk oxyamine was observed. Additionally, mixing Al(Bu-i)(3) and BIPY promo tes a variety of reactions involving alkyl and hydride transfers to th e aromatic rings forming reduced BIPY products, along with a persisten t organoaluminum radical. All these results illustrate that the proces s is considerably more complicated than postulated before. Conversely, at -78 degrees C, a single active species excluding the participation of TEMPO has been put, in evidence, displaying some ''living'' charac teristics. Several experiments support its anionic nature, as previous ly suggested by Ikeda.