Investigation of the microstructure of metallocene-catalyzed norbornene-ethylene copolymers using NMR spectroscopy

Christer H. Bergström*, Bernd R. Sperlich, Juhana Ruotoistenmäki, Jukka Seppälä

*Corresponding author for this work

    Research output: Contribution to journalArticleScientificpeer-review

    65 Citations (Scopus)

    Abstract

    Norbornene-ethylene copolymers were prepared using the metallocene catalyst ethylene bis (indenyl) zirconium dichloride with MAO, and their microstructure was characterized with 1H-NMR and 13C-NMR methods. From a Cosy 1H-NMR spectrum it was found that all norbornene units are enchained in the exo-configuration. The sequence distribution of norbornene units was investigated using 13C-1H correlations, hmqc for one-bond correlations, and hmbc for two- or three-bond correlations. It was shown that norbornene diads were formed at a high norbornene content (45 mol %). When further increasing the norbornene incorporation (66 mol %) a number of new signals were obtained. A Cosy 1H-NMR spectrum revealed a new crosspeak which, according to the corresponding 13C-NMR shifts (hmqc), correlated well with a terminal unit of a trimer of norbornene. This means that at very high norbornene contents, norbornene triads can be formed. Because the formation of isotactic norbornene triads is very difficult to understand from a sterical point of view, an epimerization process causing stereoirregularities in the norbornene triad is proposed.

    Original languageEnglish
    Pages (from-to)1633-1638
    Number of pages6
    JournalJournal of Polymer Science Part A: Polymer Chemistry
    Volume36
    Issue number10
    DOIs
    Publication statusPublished - 30 Jul 1998
    MoE publication typeA1 Journal article-refereed

    Keywords

    • Cyclic olefin copolymers
    • Metallocene catalysts
    • Microstructure
    • NMR
    • Norbornene

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