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Stereoregular and stereoirregular alternating ethylene-norbornene copolymers (Articolo in rivista)

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Stereoregular and stereoirregular alternating ethylene-norbornene copolymers (Articolo in rivista) (literal)

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Tritto I.1, Marestin C. 2, Boggioni L. 3, Sacchi M.C. 4, Brintzinger H. H. 5, Ferro D. R. 6 (2001)
Stereoregular and stereoirregular alternating ethylene-norbornene copolymers
in Macromolecules (Print); American Chemical Society, Washington (Stati Uniti d'America)
(literal)

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Tritto I.1, Marestin C. 2, Boggioni L. 3, Sacchi M.C. 4, Brintzinger H. H. 5, Ferro D. R. 6 (literal)

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Impact Factor = 3.697; Financial support from EC TMR Project Network N°ERB FMRX CT97-0116 GLASSCYCLICS (literal)

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Ethylene-norbornene (E-N) copolymers were synthesized with the C2 metallocene rac-Me2Si(2-Me-[e]-benzindenyl)2ZrCl2 (3) and with the constrained geometry Me2Si(Me4Cp)(NtBu)TiCl2 (4) in the presence of methylaluminoxane, using a variety of monomer feed compositions. Copolymers were characterized by 13C NMR spectroscopy, gel permeation chromatography, and differential scanning calorimetry. The copolymer microstructures were analyzed in detail, and the differences in sequence distribution and tacticity of the polymers were quantified. (literal)

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1,2,3,4,6 CNR; 5 Fachbereich Chemie, Universität Konstanz, D-78457 Konstanz, Germany (literal)

Titolo

Stereoregular and stereoirregular alternating ethylene-norbornene copolymers (literal)

Abstract

Ethylene-norbornene (E-N) copolymers were synthesized with the C2 metallocene rac-Me2Si(2-Me-[e]-benzindenyl)2ZrCl2 (3) and with the constrained geometry Me2Si(Me4Cp)(NtBu)TiCl2 (4) in the presence of methylaluminoxane. The E-N copolymerizations were carried out using a variety of monomer feed compositions. Copolymers were fully characterized by 13C NMR spectroscopy, gel permeation chromatography, and differential scanning calorimetry. Copolymer microstructures were analyzed in detail, through a procedure which accounts for the stoichiometric requirements of the copolymer chain as well as for the measured areas of 13C NMR signals. This analysis, which quantifies the differences in sequence distribution and tacticity of the polymers, evidenced that mainly alternating stereoregular and stereoirregular copolymers were prepared with 3 and 4, respectively. The copolymer prepared with 4 contains both meso and racemic NEN sequences and small amounts of meso and racemic NN diads, while the alternating copolymer prepared with 3 contains only meso NEN sequences and small amounts of meso NN diads. The formation of NN diads is disfavored with both catalysts. Surprisingly, a significant amount of norbornene (up to ~10%) belonging to NNN triads (T) is obtained with the C2 catalyst. (literal)

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