Broadband dielectric spectroscopy and calorimetric investigations of d-lyxose

Abstract

Using broadband dielectric spectroscopy, we have studied different types of relaxation processes, namely, primary (α), secondary (β), and another sub-Tg process called γ-process, in the supercooled state of d-lyxose, over a wide frequency (10-2-109Hz) and temperature range (120-340 K). In addition, the same sample was analyzed by differential scanning calorimeter. The temperature dependence of the relaxation times as well as the dielectric strength of different processes has been critically examined. It has been observed that the slower secondary relaxation (designated as β-) process shifts to lower frequencies with increasing applied pressure, but not the faster one. This pressure dependence indicates that the observed slower secondary relaxation (β-) is Johari-Goldstein relaxation process and faster one (γ-process) is probably the rotation of hydroxymethyl (-CH2OH) side group attached to the sugar ring, that is, of intramolecular origin. © 2011 Elsevier Ltd. All rights reserved.