Revealing spatially heterogeneous relaxation in a model nanocomposite.
J Chem Phys
; 143(19): 194704, 2015 Nov 21.
Article
em En
| MEDLINE
| ID: mdl-26590550
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 α-relaxation time near the nanoparticle grows with cooling faster than the α-relaxation time in the bulk and is â¼20 times longer at low temperatures. The interfacial layer thickness increases from â¼1.8 nm at higher temperatures to â¼3.5 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. 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.
Texto completo:
1
Coleções:
01-internacional
Base de dados:
MEDLINE
Tipo de estudo:
Prognostic_studies
Idioma:
En
Revista:
J Chem Phys
Ano de publicação:
2015
Tipo de documento:
Article
País de afiliação:
Estados Unidos