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Title: Revealing spatially heterogeneous relaxation in a model nanocomposite

Abstract

The detailed nature of spatially heterogeneous dynamics of glycerol-silica nanocomposites is unraveled by combining dielectric spectroscopy with atomistic simulation and statistical mechanical theory. Analysis of the spatial mobility gradient shows no glassy layer, but the -relaxation time near the nanoparticle grows with cooling faster than the -relaxation time in the bulk and is ~20 times longer at low temperatures. The interfacial layer thickness increases from ~1.8 nm at higher temperatures to ~3.5 nm upon cooling to near bulk T g. A real space microscopic description of the mobility gradient is constructed by synergistically combining high temperature atomistic simulation with theory. Our analysis suggests that the interfacial slowing down arises mainly due to an increase of the local cage scale barrier for activated hopping induced by enhanced packing and densification near the nanoparticle surface. As a result, the theory is employed to predict how local surface densification can be manipulated to control layer dynamics and shear rigidity over a wide temperature range.

Authors:
 [1];  [2];  [1];  [1];  [1];  [2];  [3]
  1. Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
  2. Univ. of Illinois, Urbana, IL (United States)
  3. Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Univ. of Tennessee, Knoxville, TN (United States)
Publication Date:
Research Org.:
Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). Oak Ridge Leadership Computing Facility (OLCF)
Sponsoring Org.:
USDOE Office of Science (SC)
OSTI Identifier:
1265978
Alternate Identifier(s):
OSTI ID: 1421239
Grant/Contract Number:  
AC05-00OR22725
Resource Type:
Accepted Manuscript
Journal Name:
Journal of Chemical Physics
Additional Journal Information:
Journal Volume: 143; Journal Issue: 19; 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; relaxation times; surface dynamics; nanocomposites; interface dynamics; dielectrics

Citation Formats

Cheng, Shiwang, Mirigian, Stephen, Carrillo, Jan-Michael Y., Bocharova, Vera, Sumpter, Bobby G., Schweizer, Kenneth S., and Sokolov, Alexei P. Revealing spatially heterogeneous relaxation in a model nanocomposite. United States: N. p., 2015. Web. doi:10.1063/1.4935595.
Cheng, Shiwang, Mirigian, Stephen, Carrillo, Jan-Michael Y., Bocharova, Vera, Sumpter, Bobby G., Schweizer, Kenneth S., & Sokolov, Alexei P. Revealing spatially heterogeneous relaxation in a model nanocomposite. United States. doi:10.1063/1.4935595.
Cheng, Shiwang, Mirigian, Stephen, Carrillo, Jan-Michael Y., Bocharova, Vera, Sumpter, Bobby G., Schweizer, Kenneth S., and Sokolov, Alexei P. Wed . "Revealing spatially heterogeneous relaxation in a model nanocomposite". United States. doi:10.1063/1.4935595. https://www.osti.gov/servlets/purl/1265978.
@article{osti_1265978,
title = {Revealing spatially heterogeneous relaxation in a model nanocomposite},
author = {Cheng, Shiwang and Mirigian, Stephen and Carrillo, Jan-Michael Y. and Bocharova, Vera and Sumpter, Bobby G. and Schweizer, Kenneth S. and Sokolov, Alexei P.},
abstractNote = {The detailed nature of spatially heterogeneous dynamics of glycerol-silica nanocomposites is unraveled by combining dielectric spectroscopy with atomistic simulation and statistical mechanical theory. Analysis of the spatial mobility gradient shows no glassy layer, but the -relaxation time near the nanoparticle grows with cooling faster than the -relaxation time in the bulk and is ~20 times longer at low temperatures. The interfacial layer thickness increases from ~1.8 nm at higher temperatures to ~3.5 nm upon cooling to near bulk Tg. A real space microscopic description of the mobility gradient is constructed by synergistically combining high temperature atomistic simulation with theory. Our analysis suggests that the interfacial slowing down arises mainly due to an increase of the local cage scale barrier for activated hopping induced by enhanced packing and densification near the nanoparticle surface. As a result, the theory is employed to predict how local surface densification can be manipulated to control layer dynamics and shear rigidity over a wide temperature range.},
doi = {10.1063/1.4935595},
journal = {Journal of Chemical Physics},
number = 19,
volume = 143,
place = {United States},
year = {2015},
month = {11}
}

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