MOLECULAR DYNAMICS AND GLASS-TRANSITION OF ETHYLENE GLYCOL ADSORBED IN ZEOLITES: INFLUENCE OF SURFACE-MOLECULE INTERACTIONS, TOPOLOGY, AND LOADING DEGREE
SCIE
SCOPUS
- Title
- MOLECULAR DYNAMICS AND GLASS-TRANSITION OF ETHYLENE GLYCOL ADSORBED IN ZEOLITES: INFLUENCE OF SURFACE-MOLECULE INTERACTIONS, TOPOLOGY, AND LOADING DEGREE
- Authors
- Erdem, OF; Tsuwi, J; Hong, SB; Michel, D
- Date Issued
- 2006-09
- Publisher
- ELSEVIER SCIENCE BV
- Abstract
- By means of broadband dielectric spectroscopy the molecular dynamics of glass-forming ethylene glycol (EG) adsorbed in zeolites is investigated by varying the loading degree, the type of zeolites, and the Si/Al ratio. We only concentrate to the frequency and temperature range where relaxation processes may be observed which allow conclusions about the glass-transition. Although EG molecules in the bulk liquid show a Vogel-Fulcher-Tammann (VFT) type of activation at lower temperatures, measurements for EG molecules adsorbed in NaX zeolites always follow Arrhenius-type of behaviour independent of the loading degree. This effect is explored in more detail by measuring the dielectric relaxation rate for EG adsorbed in zeolite beta, EG/beta, with different Si/Al ratios. For the case of zeolite beta with a very large Si/Al ratio, a glass-transition is observed, i.e., a VFT-type of activation is detectable. For the system EG/beta with Si/Al ratio of 56, however, a clear Arrhenius-type of activation is observed. Obviously, due to a higher number of adsorption sites, surface-molecule interactions are of greater influence and suppress the glass-transition. For EG/beta with a Si/Al ratio between 56 and infinity, there is subtle interplay between "cooperative" and "local" motions, i.e., between VFT- and Arrhenius-type of activation behaviour. (c) 2006 Elsevier Inc. All rights reserved.
- URI
- https://oasis.postech.ac.kr/handle/2014.oak/28414
- DOI
- 10.1016/j.micromeso.2006.03.036
- ISSN
- 1387-1811
- Article Type
- Article
- Citation
- MICROPOROUS AND MESOPOROUS MATERIALS, vol. 94, no. 1-3, page. 261 - 268, 2006-09
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