Ab initio molecular modeling of 13C NMR chemical shifts of polymers. 1. Ethylene-norbornene copolymers

Paola Carbone, Mikhayl F. Budyka, Tatyana S. Zyubina, Alexander G. Ryabenko

    Research output: Contribution to journalArticlepeer-review

    Abstract

    Cycloolefin copolymers (COC) have recently raised much interest because of their excellent thermal and optical properties, largely determined by the chain composition and stereochemistry. Previous force-field computations allowed us to define the main conformational characteristics of ethylene-norbornene (E-N) copolymers and to contribute to the elucidation of their microstructure on the basis of empirical relationships between conformation and 13C nuclear magnetic resonance (NMR) chemical shifts. A thorough test of ab initio 13C chemical shifts computations [gauge-invariant atomic orbitals (GIAO)] on known cases shows that the agreement with experimental data is quite good, especially with the MPW1PW91 density functional theory (DFT), using the 6-311 + G(2d,p) basis set on properly energy-minimized structures. We applied this method on proper model compounds to confirm the signal assignment of the spectra of E-N copolymers in the presence of norbornene microblocks, where strong effects arising from ring distortions are expected to occur. The results nicely confirm the latest assignment of norbornene signals belonging to ENNE sequences. This shows the great potentialities of GIAO/DFT computations with regard to complex spectra interpretation and polymer microstructural investigations.
    Original languageEnglish
    Pages (from-to)663-669
    Number of pages6
    JournalInternational Journal of Quantum Chemistry
    Volume88
    Issue number5
    DOIs
    Publication statusPublished - 20 Jun 2002

    Keywords

    • Ab initio
    • Chemical shifts
    • Cycloolefin copolymers

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