Untersuchungen von Zuckergläsern mittels dynamischer Festkörper-NMR
We report on the application of one dimensional exchange methods to glassy Methyl -L-Rhamnopyranoside(Me Rha). This material has been thoroughly characterised in the glassy and crystalline states by proton NMR relaxation time measurements over a wide range of temperatures. Results from these measurements are consistent with other correlation time measurements for protons 3,7 which suggest that a simple single correlation time model adequately explains the data in the glassy state. The only evidence for more complex behaviour is observed above the glass transition temperature of Me Rha where anisotropic motion of the whole molecules gave way to a less anisotropic motion about 50k above the glass transition temperature. These results appear to be counter intuitive. It would be expected that an amorphous materials such as a glass would show a distribution of correlation times. However, although the 2D experiments described above did show a distribution slightly above Tg, until now there has been no report examining slow motions of sugars in the glassy state.
Dynamische Festkörper-NMR, Zucker
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