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Title: Theory of activated glassy relaxation, mobility gradients, surface diffusion, and vitrification in free standing thin films

Abstract

Here, we have constructed a quantitative, force level, statistical mechanical theory for how confinement in free standing thin films introduces a spatial mobility gradient of the alpha relaxation time as a function of temperature, film thickness, and location in the film. The crucial idea is that relaxation speeds up due to the reduction of both near-surface barriers associated with the loss of neighbors in the local cage and the spatial cutoff and dynamical softening near the vapor interface of the spatially longer range collective elasticity cost for large amplitude hopping. These two effects are fundamentally coupled. Quantitative predictions are made for how an apparent glass temperature depends on the film thickness and experimental probe technique, the emergence of a two-step decay and mobile layers in time domain measurements, signatures of confinement in frequencydomain dielectric loss experiments, the dependence of film-averaged relaxation times and dynamic fragility on temperature and film thickness, surface diffusion, and the relationship between kinetic experiments and pseudo-thermodynamic measurements such as ellipsometry.

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:
1265980
DOE Contract Number:  
AC05-00OR22725
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of Chemical Physics; Journal Volume: 143; Journal Issue: 24
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; 37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY

Citation Formats

Mirigian, Stephen, and Schweizer, Kenneth S. Theory of activated glassy relaxation, mobility gradients, surface diffusion, and vitrification in free standing thin films. United States: N. p., 2015. Web. doi:10.1063/1.4937953.
Mirigian, Stephen, & Schweizer, Kenneth S. Theory of activated glassy relaxation, mobility gradients, surface diffusion, and vitrification in free standing thin films. United States. doi:10.1063/1.4937953.
Mirigian, Stephen, and Schweizer, Kenneth S. Thu . "Theory of activated glassy relaxation, mobility gradients, surface diffusion, and vitrification in free standing thin films". United States. doi:10.1063/1.4937953.
@article{osti_1265980,
title = {Theory of activated glassy relaxation, mobility gradients, surface diffusion, and vitrification in free standing thin films},
author = {Mirigian, Stephen and Schweizer, Kenneth S.},
abstractNote = {Here, we have constructed a quantitative, force level, statistical mechanical theory for how confinement in free standing thin films introduces a spatial mobility gradient of the alpha relaxation time as a function of temperature, film thickness, and location in the film. The crucial idea is that relaxation speeds up due to the reduction of both near-surface barriers associated with the loss of neighbors in the local cage and the spatial cutoff and dynamical softening near the vapor interface of the spatially longer range collective elasticity cost for large amplitude hopping. These two effects are fundamentally coupled. Quantitative predictions are made for how an apparent glass temperature depends on the film thickness and experimental probe technique, the emergence of a two-step decay and mobile layers in time domain measurements, signatures of confinement in frequencydomain dielectric loss experiments, the dependence of film-averaged relaxation times and dynamic fragility on temperature and film thickness, surface diffusion, and the relationship between kinetic experiments and pseudo-thermodynamic measurements such as ellipsometry.},
doi = {10.1063/1.4937953},
journal = {Journal of Chemical Physics},
number = 24,
volume = 143,
place = {United States},
year = {Thu Jan 01 00:00:00 EST 2015},
month = {Thu Jan 01 00:00:00 EST 2015}
}