Effects of water on the primary and secondary relaxation of xylitol and sorbitol: implication on the origin of the Johari-Goldstein relaxation.
Dielectric spectroscopy was employed to study the effects of water on the primary alpha -relaxation and the secondary beta -relaxation of xylitol. The measurements were made on anhydrous xylitol and mixtures of xylitol with water with three different water concentrations over a temperature range from 173 K to 293 K. The alpha -relaxation speeds up with increasing concentration of water in xylitol, whereas the rate of the beta -relaxation is essentially unchanged. Some systematic differences in the behavior of alpha -relaxation for anhydrous xylitol and the mixtures were observed. Our findings confirm all the observations of Nozaki et al. [J. Non-Cryst. Solids 307, 349 (2002)]] in sorbitol/water mixtures. Effects of water on both the alpha - and beta -relaxation dynamics in xylitol and sorbitol are explained by using the coupling model.
Psurek
T
T
Institute of Physics, Silesian University, ul. Uniwersytecka 4, 40-007 Katowice, Poland.
Maslanka
S
S
Paluch
M
M
Nozaki
R
R
Ngai
K L
KL