Highly active methyl methacrylate polymerization catalysts obtained from bis(3,5‐dinitro‐salicylaldiminate)nickel(II) complexes and methylaluminoxane

Abstract

AbstractThe homopolymerization of methyl methacrylate was investigated with bis(salicylaldiminate)nickel(II) complexes, such as bis[3,5‐dinitro‐N(2,6‐diisopropylphenyl)salicylaldiminate]nickel(II) (IIIa) and bis[3,5‐dinitro‐N(phenyl)salicylaldiminate]nickel(II) (IIIb), and with methylaluminoxane (MAO) as an activator. In particular, the effect of the Al/Ni molar ratio on the catalytic activity and on the properties of the resulting poly(methyl methacrylate) (PMMA) was checked. The maximum activity was ascertained when an Al/Ni molar ratio equal to about 100 was used. However, the productivity of the catalytic systems was rather low. When the IIIa/MAO catalytic system was prepared under an ethylene atmosphere, an extremely high activity was observed, a productivity value of up to around 150,000 g of PMMA/(mol of Ni × h) being obtained, the highest ever found with nickel‐based catalysts. No appreciable presence of ethylene counits in the polymeric products was also ascertained. When the IIIb/MAO system was used, similar results were found, and high molecular weight PMMAs were obtained, despite the absence of bulky isopropyl substituents in positions ortho and ortho′ to the N‐aryl moiety of the salicylaldiminate ligand. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 2117–2124, 2003