| Abstract
| - Molecular mobility in crystalline anhydrous caffeine was studied by the dielectric technique of thermallystimulated depolarization currents (TSDC). Two relaxational processes were found, one appearing at ∼ −10°C that is ascribed to a reorientational glass transition, and a higher temperature one that probably arisesfrom local molecular motions that are precursors of diffusion and sublimation. The experimental results suggestthat both crystalline phases II and I of caffeine, that have distinct crystal structures, are solid rotator phases.Furthermore, this dynamic reorientational disorder shows a reorientational glass transition at the sametemperature in phase II and in metastable phase I.
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