TY - JOUR
T1 - Experimental studies of Debye-like process and structural relaxation in mixtures of 2-ethyl-1-hexanol and 2-ethyl-1-hexyl bromide
AU - Preu, M.
AU - Gainaru, C.
AU - Hecksher, T.
AU - Bauer, S.
AU - Dyre, J. C.
AU - Richert, Ranko
AU - Böhmer, R.
N1 - Funding Information:
We thank H. J. Weber for his help with the NIR spectrometer. This project was financially supported by the Deutsche Forschungsgemeinschaft under Grant No. BO1301/8 which is highly appreciated. This material is partly based upon the work supported by the National Science Foundation under Grant No. CHE 1026124. The center for viscous liquid dynamics Glass and Time is sponsored by the Danish National Research Foundation (DNRF).
Copyright:
Copyright 2012 Elsevier B.V., All rights reserved.
PY - 2012/10/14
Y1 - 2012/10/14
N2 - Binary solutions of 2-ethyl-1-hexanol (2E1H) with 2-ethyl-1-hexyl bromide (2E1Br) are investigated by means of dielectric, shear mechanical, near-infrared, and solvation spectroscopy as well as dielectrically monitored physical aging. For moderately diluted 2E1H the slow Debye-like process, which dominates the dielectric spectra of the neat monohydroxy alcohol, separates significantly from the α-relaxation. For example, the separation in equimolar mixtures amounts to four decades in frequency. This situation of highly resolved processes allows one to demonstrate unambiguously that physical aging is governed by the α-process, but even under these ideal conditions the Debye process remains undetectable in shear mechanical experiments. Furthermore, the solvation experiments show that under constant charge conditions the microscopic polarization fluctuations take place on the time scale of the structural process. The hydrogen-bond populations monitored via near-infrared spectroscopy indicate the presence of a critical alcohol concentration, x c ≈ 0.5-0.6, thereby confirming the dielectric data. In the pure bromide a slow dielectric process of reduced intensity is present in addition to the main relaxation. This is taken as a sign of intermolecular cooperativity probably mediated via halogen bonds.
AB - Binary solutions of 2-ethyl-1-hexanol (2E1H) with 2-ethyl-1-hexyl bromide (2E1Br) are investigated by means of dielectric, shear mechanical, near-infrared, and solvation spectroscopy as well as dielectrically monitored physical aging. For moderately diluted 2E1H the slow Debye-like process, which dominates the dielectric spectra of the neat monohydroxy alcohol, separates significantly from the α-relaxation. For example, the separation in equimolar mixtures amounts to four decades in frequency. This situation of highly resolved processes allows one to demonstrate unambiguously that physical aging is governed by the α-process, but even under these ideal conditions the Debye process remains undetectable in shear mechanical experiments. Furthermore, the solvation experiments show that under constant charge conditions the microscopic polarization fluctuations take place on the time scale of the structural process. The hydrogen-bond populations monitored via near-infrared spectroscopy indicate the presence of a critical alcohol concentration, x c ≈ 0.5-0.6, thereby confirming the dielectric data. In the pure bromide a slow dielectric process of reduced intensity is present in addition to the main relaxation. This is taken as a sign of intermolecular cooperativity probably mediated via halogen bonds.
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U2 - 10.1063/1.4755754
DO - 10.1063/1.4755754
M3 - Article
C2 - 23061850
AN - SCOPUS:84867544010
VL - 137
JO - Journal of Chemical Physics
JF - Journal of Chemical Physics
SN - 0021-9606
IS - 14
M1 - 144502
ER -