Living polymerization of methacrylic esters with aluminium porphyrin initiators. Axial ligand exchange activities of alkyl‐ and enolate‐aluminium porphyrins in relation to the polymerization Mechanism

Abstract

AbstractPolymerization 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‐tetramethyl‐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. 1H 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‐d8), 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.