Dynamics of the slow mode in the family of six-carbon monosaccharides monitored bydielectric spectroscopy

Abstract

Broadband dielectric measurements performed on D-glucose, L-sorbose, D-fructose andD-galactose revealed that, except for the structural relaxation process, one can detect inthe liquid phase of these carbohydrates a much slower relaxation mode. Recently we havedemonstrated that in D-glucose this relaxation mode might be related to the long rangecorrelation of density fluctuations (LRCDF), also called Fischer clusters (FC).Based on the dielectric data obtained for the four monosaccharides we were ableto make a more general conclusion about the characteristic dielectric featuresof the slow mode in the whole family of carbohydrates. We found out that thetimescale separation between structural and considered relaxation reaches up to sixdecades at the glass transition temperature and the dielectric strength decreasessignificantly with lowering temperature. Another very interesting feature of the slowprocess is that it can be described by an almost exponential response function.We have found out that the fragility of the slow process lies within the rangem = 44–50. Finally, we have also shown that there is a close link between structural and slowrelaxation.