Analysis of cross-polarization dynamics between H-1 and F-19 in Viton fluoroelastomer using solid-state F-19 magic angle spinning and H-1 -> F-19 cross-polarization magic angle spinning NMR

Citation
S. Ando et al., Analysis of cross-polarization dynamics between H-1 and F-19 in Viton fluoroelastomer using solid-state F-19 magic angle spinning and H-1 -> F-19 cross-polarization magic angle spinning NMR, MAGN RES CH, 37(10), 1999, pp. 709-720
Citations number
21
Categorie Soggetti
Spectroscopy /Instrumentation/Analytical Sciences
Journal title
MAGNETIC RESONANCE IN CHEMISTRY
ISSN journal
07491581 → ACNP
Volume
37
Issue
10
Year of publication
1999
Pages
709 - 720
Database
ISI
SICI code
0749-1581(199910)37:10<709:AOCDBH>2.0.ZU;2-H
Abstract
The cross-polarization dynamics between H-1 and F-19 in a Viton-type fluoro elastomer were studied using F-19 magic angle spinning (MAS) and H-1 --> F- 19 cross-polarization (CP)/MAS NMR at 188.29 MHz. The phenomenological theo ry of spin thermodynamics based on the spin temperature hypothesis was empl oyed to describe the polarization transfer between the H-1 and F-19 spin ba ths. 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(H) and T-1 rho(F) for five separate peaks in the F-19 spectra. The values of T-1 rho(H) and T-1 rho(F) obtained are consistent with those independently measured by spin-locking experiments. The true values of THF 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. Th e temperature dependences of T-1(F) and T-1 rho(F) were measured between -4 9 and 86 degrees C. The relationship between the CP dynamics parameters and the local molecular motion in the polymer chains is discussed. Copyright ( C) 1999 John Wiley & Sons, Ltd.