8th Liquid Matter Conference September 6-10, 2011 Wien, Austria ...

Tue 611:23-14:00P2.21Glass transition and relaxation processes in xylitol-watermixturesKhalid Elamin, 1 Johan Sjöström, 1 Helén Jansson, 1 and Jan Swenson 11 Chalmers University of Technology, Chalmers University of Technology, Applied Physics,SE-412 96 Goteborg, Sweden SE-412 96 Goteborg, Goteborg, SwedenDielectric spectroscopy and differential scanning calorimetry (DSC) were employed to studysupercooled xylitol mixed with water in a wide frequency range (10 −2 − 106 Hz) and at differenttemperatures (120 − 365 K). The presence of water clearly has an effect on both the cooperativeα-relaxation and the secondary β-relaxation. The α-relaxation, which shows non-Arrheniustemperature dependence, becomes faster with increasing concentration of water. The secondaryβ-relaxation shows Arrhenius temperature dependence and the intensity increases dramaticallywith increasing water concentration. We find one calormetric glass transition over the wholeconcentration range. It decreases from 247 K for pure xylitol to about 181 K at a water concentrationof about 37 wt%. At higher water concentrations ice is formed and the glass transitiontemperature increases to a steady value of about 200 K for all higher water concentrations. ThisT g corresponds to an unfrozen xylitol-water solution containing 20 wt% water. In addition to thetrue glass transition we observed a glass transition-like feature at 220 K for all the ice containingsamples. However, this feature is more likely due ice dissolution [1].[1] Akira Inaba, Ove Andersson, Thermochimica Acta, 461, 44 (2007).21