LIVING POLYMERIZATION OF METHACRYLIC ESTERS WITH ALUMINUM PORPHYRIN INITIATORS - AXIAL LIGAND-EXCHANGE ACTIVITIES OF ALKYL-ALUMINUM AND ENOLATE-ALUMINUM PORPHYRINS IN RELATION TO THE POLYMERIZATION MECHANISM

Polymerization of methacrylic esters such as benzyl methacrylate using as initiator an equimolar mixture of methylaluminium 5,10,15,20-tetraphenylporphine [(TPP)AlMe] and 2,7,12,17-tetramethy1-3,8,13,18-tetramethylporphine [(EtioP)AlMe] proceeded from both initiators, affording a unimodal polymer of narrow molecular weight distribution, although the reactivities of (TPP)AlMe and (EtioP)AlMe are very different from each other. H-1 NMR studies on a mixture of two different (porphinato)aluminium enolates, the growing species, and a mixture of a (porphinato)aluminium enolate and an alcoholate, in the absence and presence of methyl methacrylate (MMA or MMA-d(g)), indicated an acyclic transition state polymerization mechanism by the participation of two aluminium porphyrin molecules, where the growing species always exchange their enolate ligands whenever it grows.