Glycerol confined in zeolitic imidazolate frameworks: The temperature-dependent cooperativity length scale of glassy freezing

Glycerol confined in zeolitic imidazolate frameworks: The temperature-dependent cooperativity length scale of glassy freezing

In the present work, we employ broadband dielectric spectroscopy to study the molecular dynamics of the prototypical glass former glycerol confined in two microporous zeolitic imidazolate frameworks (ZIF-8 and ZIF-11) with well-defined pore diameters of 1.16 and 1.46 nm, respectively. The spectra re...

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Bibliographic Details
Published in:The Journal of chemical physics 2019-01, Vol.150 (2), p.024504-024504
Main Authors: Uhl, M., Fischer, J. K. H., Sippel, P., Bunzen, H., Lunkenheimer, P., Volkmer, D., Loidl, A.
Format: Article
Language:eng
Subjects:
Broadband
Chain dynamics
Divergence
Dynamic tests
Freezing
Glass transition temperature
Glycerol
Metal-organic frameworks
Molecular dynamics
Molecular motion
Phase transitions
Pore size
Porosity
Spectrum analysis
Temperature
Temperature dependence
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Summary:In the present work, we employ broadband dielectric spectroscopy to study the molecular dynamics of the prototypical glass former glycerol confined in two microporous zeolitic imidazolate frameworks (ZIF-8 and ZIF-11) with well-defined pore diameters of 1.16 and 1.46 nm, respectively. The spectra reveal information on the modified α relaxation of the confined supercooled liquid, whose temperature dependence exhibits clear deviations from the typical super-Arrhenius temperature dependence of the bulk material, depending on the temperature and pore size. This allows assigning well-defined cooperativity length scales of molecular motion to certain temperatures above the glass transition. We relate these and previous results on glycerol confined in other host systems to the temperature-dependent length scale deduced from nonlinear dielectric measurements. The combined experimental data can be consistently described by a critical divergence of this correlation length as expected within theoretical approaches assuming that the glass transition is due to an underlying phase transition.
ISSN:0021-9606
1089-7690