The methyl group as a built-in probe of the glassy dynamics in propylene carbonate
2001
Deuteron
nuclear magnetic resonance was employed to study primarily the glassy phase of the fragile glass-former
propylene carbonate, selectively deuterated at the methyl group. The analysis of temperature dependent
line shapes allowed us to map out the energy barrier distribution below the glass transition temperature.
The results were compared to measurements of spin-relaxation times. We determined the relative width of the
barrier distribution and the extent of the decoupling between the methyl group rotation time and the structural
relaxation time near the glass transition. These findings are discussed in the context of what has been
reported for secondary relaxation processes in other glass-formers. Stimulated echo experiments on propylene
carbonate demonstrate that, while in the supercooled liquid small
angle reorientations
dominate, in the glass
the methyl group performs 120° (or 60°) jumps.
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