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Ab initio Molecular Modeling of 13C NMR Chemical Shifts of Polymers. 1. Ethylene-Norbornene Copolymers (Articolo in rivista)
- Type
- Label
- Ab initio Molecular Modeling of 13C NMR Chemical Shifts of Polymers. 1. Ethylene-Norbornene Copolymers (Articolo in rivista) (literal)
- Anno
- 2002-01-01T00:00:00+01:00 (literal)
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- Ragazzi M., Carbone P., Ferro D.R. (literal)
- Pagina inizio
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- Rivista
- Note
- ISI Web of Science (WOS) (literal)
- Titolo
- Ab initio Molecular Modeling of 13C NMR Chemical Shifts of Polymers. 1. Ethylene-Norbornene Copolymers (literal)
- Abstract
- Cicloolefin 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
torough 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 MPW1PW1 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. (literal)
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