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Analysis of cross‐polarization dynamics between 1 H and 19 F in Viton fluoroelastomer using solid‐state 19 F magic angle spinning and 1 H → 19 F cross‐polarization magic angle spinning NMR
Author(s) -
Ando Shinji,
Harris Robin K.,
Monti Gustavo A.,
Reinsberg Stefan A.
Publication year - 1999
Publication title -
magnetic resonance in chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.483
H-Index - 72
eISSN - 1097-458X
pISSN - 0749-1581
DOI - 10.1002/(sici)1097-458x(199910)37:10<709::aid-mrc524>3.0.co;2-g
Subject(s) - magic angle spinning , chemistry , polarization (electrochemistry) , spinning , magic angle , magnetization transfer , fluorine 19 nmr , spectral line , spin polarization , thermodynamics , physics , nuclear magnetic resonance spectroscopy , stereochemistry , polymer chemistry , nuclear physics , quantum mechanics , medicine , magnetic resonance imaging , radiology , electron
Abstract The cross‐polarization dynamics between 1 H and 19 F in a Viton‐type fluoroelastomer were studied using 19 F magic angle spinning (MAS) and 1 H → 19 F cross‐polarization (CP)/MAS NMR at 188.29 MHz. The phenomenological theory of spin thermodynamics based on the spin temperature hypothesis was employed to describe the polarization transfer between the 1 H and 19 F spin baths. Simultaneous fitting of the evolution of magnetization in the standard CP and a modified CP(TORQUE) experiment, using the exact solutions of the equations for the spin thermodynamics, gave unique sets of the parameters T HF , $T_{1\rho}^{\rm H}$ and $T_{1\rho}^{\rm F}$ for five separate peaks in the 19 F spectra. The values of $T_{1\rho}^{\rm H}$ and $T_{1\rho}^{\rm F}$ obtained are consistent with those independently measured by spin‐locking experiments. The true values of T HF are significantly larger (by a factor of ca. 4) than those derived from a simple two‐parameter fit of the CP behaviour with variable contact time.The temperature dependences of $T^{\rm F}_{1}$ and $T^{\rm F}_{1\rho}$ were measured between −49 and 86 °C. The relationship between the CP dynamics parameters and the local molecular motion in the polymer chains is discussed. Copyright © 1999 John Wiley & Sons, Ltd.