The β-α branching in D-sorbitol as studied by thermally stimulated depolarization currents (TSDC)

The molecular motions in D-sorbitol (D-glucitol) have been studied by thermally stimulated depolarization currents (TSDC) in the temperature region between -160 and 10 degreesC. The beta relaxation appears as a broad global peak between -160 and -50 degreesC and its features were compared with those of the beta relaxation of maltitol (a D-glucitol derivative). A study of the alpha relaxation of sorbitol, which shows a maximum intensity at approximately -1 degreesC, is also presented, and from the obtained data, the fragility index of this glass former is calculated. The alpha and beta relaxations are observed to merge in the frequency window of the TSDC technique, and it is underlined that this merging is a consequence of the overlap of the tails of these distributions in this frequency window. In this context, the merging observed by TSDC images the branching of the most probable times of the two distributions predicted by dielectric relaxation spectroscopy at the branching temperature T alpha beta.