The slow molecular mobility in amorphous trehalose.

The molecular mobility in amorphous trehalose is studied by thermally stimulated depolarisation currents (TSDC). The effect of aging on the sub-T(g) motional processes was analysed during annealing at a given aging temperature, some degrees below the calorimetric glass transition temperature T(g)=115 degrees C. The features of different motional components of the secondary relaxation are monitored as a function of time as the glass structurally relaxes on aging. The faster components of the secondary relaxation are negligibly dependent on aging and may be ascribed to intramolecular modes of motion, while the slower motional modes show a significant dependence on aging consisting of some kind of local motions with some intermolecular nature. The dielectric strength of this relaxation decreases with increasing aging time, and there is no evidence for any modification with aging of the relaxation time of this local mobility. The TSDC study of the molecular mobility of amorphous trehalose in the temperature region of the glass transformation provides the unexpected result that no glass transition signal is observable in this temperature region.