Does the arrhenius temperature dependence of the Johari-Goldstein relaxation persist above T(g)?
Dielectric spectra of the polyalcohols sorbitol and xylitol were measured under isobaric pressures up to 1.8 GPa. At elevated pressure, the separation between the alpha and beta relaxation peaks is larger than at ambient pressure, enabling the beta relaxation times to be unambiguously determined. Taking advantage of this, we show that the Arrhenius temperature dependence of the beta relaxation time does not persist for temperatures above T(g). This result, consistent with inferences drawn from dielectric relaxation measurements at ambient pressure, is obtained directly, without the usual problematic deconvolution the beta and alpha processes.
Paluch
M
M
Institute of Physics, Silesian University, ul. Uniwersytecka 4, 40-007 Katowice, Poland.
Roland
C M
CM
Pawlus
S
S
Zioło
J
J
Ngai
K L
KL