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Glass Transition in Sub-nanometer Confinement

Published online by Cambridge University Press:  10 February 2011

A. Huwe
Affiliation:
University of Leipzig, Department of Physics, D - 04103 Leipzig, Germany
F. Kremer
Affiliation:
University of Leipzig, Department of Physics, D - 04103 Leipzig, Germany
M. Arndt
Affiliation:
University of Leipzig, Department of Physics, D - 04103 Leipzig, Germany
P. Behrens
Affiliation:
University of Hannover, Institute of Inorganic Chemistry, D - 30167 Hannover, Germany
W. Schwieger
Affiliation:
University Erlangen-Nürnberg, D - 91058 Erlangen, Germany
G. Ihlein
Affiliation:
Max Planck Institute of Coal Research, D - 45470 Mülheim / Ruhr, Germany
Ö. Akdogan
Affiliation:
Max Planck Institute of Coal Research, D - 45470 Mülheim / Ruhr, Germany
F. Schüth
Affiliation:
Max Planck Institute of Coal Research, D - 45470 Mülheim / Ruhr, Germany
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Abstract

Broadband dielectric spectroscopy (10−2 Hz - 109Hz) is employed to study the molecular dynamics of low-molecular-weight glassforming liquids being confined to nanopores. For the H-bond forming liquid propylene glycol being confined to (uncoated and silanized) nanopores (pore size: 2.5 nm, 5.0 nm and 7.5 nm) a molecular dynamics is observed which is comparable to that of the bulk liquid. Due to surface effects in uncoated nanopores the relaxation time distribution is broadened on the long term side and the mean relaxation rate is decreased by about half a decade. This effect can be counterbalanced by lubricating the inner surfaces of the pores resulting in a relaxation rate which is slightly faster compared to the bulk liquid. For the H-bonded liquid ethylene glycol (EG) embedded in zeolites of different pore size and topology one observes a sharp transition from a single-molecule dynamics to that of a liquid depending on the coordination number of the confined molecules. While EG in silicalite (showing a single molecule relaxation) has four neighboring molecules, EG in zeolite beta or AIPO4-5 has a coordination number of five and behaves like a bulk liquid.

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Type
Research Article
Copyright
Copyright © Materials Research Society 1999

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