MECHANISM OF ANIONIC-POLYMERIZATION OF METHYL-METHACRYLATE IN THE PRESENCE OF ALUMINUM ALKYLS

A bimetallic aluminate complex ('ate' complex) is regarded to be the a ctive species in the anionic polymerization of MMA in the presence of aluminium alkyls in toluene. The aluminate end group is supposed to be able to coordinate to the penultimate end group of the polymer chain. As a result, the rate of polymerization is significantly slower than for aluminium-free polymerization. Excess aluminium alkyl (AI/Li > 1) coordinates to the ester carbonyl groups of monomer and polymer, but t here is no evidence for an activated monomer mechanism. To a small ext ent, the polymerization at -78 degrees C is accompanied by side reacti ons (e.g. formation of vinyl ketones) but nevertheless it has a certai n living character.