TY - JOUR
T1 - Dynamics of glass-forming liquids. XIV. A search for ultraslow dielectric relaxation in glycerol
AU - Richert, Ranko
PY - 2010/8/21
Y1 - 2010/8/21
N2 - A recent dielectric study of various polyalcohols reported on the general occurrence of an ultraslow process with Debye type character in hydrogen bonded liquids [R. Bergman, H. Jansson, and J. Swenson, J. Chem. Phys. 132, 044504 (2010)], whereas previous work suggested that such behavior is specific to monoalcohols only. Clarifying this issue is highly relevant for assessing models aimed at rationalizing these modes that are slower than the primary structural relaxation and associated with a single time constant. To this end, the dielectric relaxation of glycerol is measured at different electrode distances with high accuracy. In this manner, electrode polarization can be separated from the dielectric signals intrinsic in the supercooled liquid. In the frequency range below the loss peak frequency ωmax of the α -process, only dc-conductivity is required to understand the dielectric properties of supercooled glycerol within a margin of ε″ ≈±0.1 and thus no indication of an ultraslow peak is found. More quantitatively, any dielectric Debye like mode located around 10-5 ωmax would need to have an amplitude smaller than 0.4% of that of the primary dielectric process to be consistent with the present findings, in contrast to previous claims of >50%.
AB - A recent dielectric study of various polyalcohols reported on the general occurrence of an ultraslow process with Debye type character in hydrogen bonded liquids [R. Bergman, H. Jansson, and J. Swenson, J. Chem. Phys. 132, 044504 (2010)], whereas previous work suggested that such behavior is specific to monoalcohols only. Clarifying this issue is highly relevant for assessing models aimed at rationalizing these modes that are slower than the primary structural relaxation and associated with a single time constant. To this end, the dielectric relaxation of glycerol is measured at different electrode distances with high accuracy. In this manner, electrode polarization can be separated from the dielectric signals intrinsic in the supercooled liquid. In the frequency range below the loss peak frequency ωmax of the α -process, only dc-conductivity is required to understand the dielectric properties of supercooled glycerol within a margin of ε″ ≈±0.1 and thus no indication of an ultraslow peak is found. More quantitatively, any dielectric Debye like mode located around 10-5 ωmax would need to have an amplitude smaller than 0.4% of that of the primary dielectric process to be consistent with the present findings, in contrast to previous claims of >50%.
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U2 - 10.1063/1.3473814
DO - 10.1063/1.3473814
M3 - Article
C2 - 20726647
AN - SCOPUS:77956085280
SN - 0021-9606
VL - 133
JO - Journal of Chemical Physics
JF - Journal of Chemical Physics
IS - 7
M1 - 074502
ER -