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Title: Communication: slow relaxation, spatial mobility gradients, and vitrification in confined films

Abstract

Two decades of experimental research indicate that spatial confinement of glass-forming molecular and polymeric liquids results in major changes of their slow dynamics beginning at large confinement distances. A fundamental understanding remains elusive given the generic complexity of activated relaxation in supercooled liquids and the major complications of geometric confinement, interfacial effects, and spatial inhomogeneity. For this research, we construct a predictive, quantitative, force-level theory of relaxation in free-standing films for the central question of the nature of the spatial mobility gradient. The key new idea is that vapor interfaces speed up barrier hopping in two distinct, but coupled, ways by reducing near surface local caging constraints and spatially long range collective elastic distortion. Effective vitrification temperatures, dynamic length scales, and mobile layer thicknesses naturally follow. In conclusion, our results provide a unified basis for central observations of dynamic and pseudo-thermodynamic measurements.

Authors:
 [1];  [1]
  1. Univ. of Illinois, Urbana, IL (United States)
Publication Date:
Research Org.:
Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
Sponsoring Org.:
USDOE Office of Science (SC)
OSTI Identifier:
1265311
DOE Contract Number:  
AC05-00OR22725
Resource Type:
Journal Article
Journal Name:
Journal of Chemical Physics
Additional Journal Information:
Journal Volume: 141; Journal Issue: 16; Journal ID: ISSN 0021-9606
Publisher:
American Institute of Physics (AIP)
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; 37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY; surface dynamics; glass transitions; relaxation times; free surface; elasticity theory

Citation Formats

Mirigian, Stephen, and Schweizer, Kenneth S. Communication: slow relaxation, spatial mobility gradients, and vitrification in confined films. United States: N. p., 2014. Web. doi:10.1063/1.4900507.
Mirigian, Stephen, & Schweizer, Kenneth S. Communication: slow relaxation, spatial mobility gradients, and vitrification in confined films. United States. doi:10.1063/1.4900507.
Mirigian, Stephen, and Schweizer, Kenneth S. Fri . "Communication: slow relaxation, spatial mobility gradients, and vitrification in confined films". United States. doi:10.1063/1.4900507. https://www.osti.gov/servlets/purl/1265311.
@article{osti_1265311,
title = {Communication: slow relaxation, spatial mobility gradients, and vitrification in confined films},
author = {Mirigian, Stephen and Schweizer, Kenneth S.},
abstractNote = {Two decades of experimental research indicate that spatial confinement of glass-forming molecular and polymeric liquids results in major changes of their slow dynamics beginning at large confinement distances. A fundamental understanding remains elusive given the generic complexity of activated relaxation in supercooled liquids and the major complications of geometric confinement, interfacial effects, and spatial inhomogeneity. For this research, we construct a predictive, quantitative, force-level theory of relaxation in free-standing films for the central question of the nature of the spatial mobility gradient. The key new idea is that vapor interfaces speed up barrier hopping in two distinct, but coupled, ways by reducing near surface local caging constraints and spatially long range collective elastic distortion. Effective vitrification temperatures, dynamic length scales, and mobile layer thicknesses naturally follow. In conclusion, our results provide a unified basis for central observations of dynamic and pseudo-thermodynamic measurements.},
doi = {10.1063/1.4900507},
journal = {Journal of Chemical Physics},
issn = {0021-9606},
number = 16,
volume = 141,
place = {United States},
year = {2014},
month = {10}
}

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