Ethene/Norbornene Copolymerization using the Catalyst System Pr^<i>i</i>[(3‐Pr^<i>i</i>‐Cp)Flu]ZrCl₂: Determination of the Copolymerization Parameters and Mechanistic Considerations

Abstract

Abstract The 13 C NMR spectra of ethene/norbornene copolymers in which there are no norbornene microblocks are much simpler than those of copolymers in which norbornene microblocks are present, making it possible to completely assign all the 13 C resonances to the corresponding pentads in the copolymer chain. However, there is disagreement in the literature over several assignments of the ethene 13 C NMR signals. In this paper these discrepancies are summarized and discussed. This contribution also reports ethene/norbornene copolymerizations carried out at various temperatures using the homogeneous catalyst system Pr i [(3‐Pr i ‐Cp)Flu]ZrCl 2 . The 13 C NMR spectra of the copolymers were analyzed in the light of the discussion above and the triad distributions were used to determine the copolymerization parameters by Markov first‐ and second‐order statistical models. On the basis of these results, the mechanism generating such an alternating microstructure in these copolymers is discussed and compared with the mechanism previously proposed in the literature. The 13 C NMR spectrum with signal assignments of an ethene/norbornene copolymer without norbornene microblocks. magnified image The 13 C NMR spectrum with signal assignments of an ethene/norbornene copolymer without norbornene microblocks.