NMR Studies on the Propagation Mechanisms of Methyl Methacrylate Polymerization with Alkyl-Iron and Cobalt Complexes

Abstract

Stereochemical configurations of poly(methyl methacrylate)s prepared with alkylbis(dipyridyl)cobalt and dialkylbis(dipyridyl)iron were studied by NMR spectroscopy. From the dyad, triad, and tetrad information of poly(methyl methacrylate)s prepared with the alkyl-transition metal catalysts, the propagation mechanisms giving acetone-soluble and acetone-insoluble polymers were studied. The process forming the acetone-soluble polymer was found to follow the Bernoulli trial statistics. The acetone-insoluble polymer which was prepared with FeEt2(dipy)2 in solvents of weak coordinating ability was found to be a stereoblock type and to obey the first-order Markovian statistics. The penultimate and pen-penultimate effects were estimated for the two types of polymerization processes, and the role of solvents in the propagation mechanisms is discussed. The results are consistent with the coordinated anionic mechanism and a possible model for the propagating species to satisfy these results is proposed.