Geometrical confinement and cooperativity in supercooled liquids studied by solvation dynamics

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Abstract

The molecular dynamics of supercooled liquids confined to the mesopores of sol-gel glasses are interpreted in terms of the spatial competition between the average length scale of cooperativity assumed to increase with time and the geometrical confinement on scales between 2.5 and 7.5 nm. Opposed to relating the fast and slow relaxation components to spatially distinct regimes, the picture of a mesoscopically uniform but cooperative relaxation as stimulated by the theoretical work of Jäckle is proposed. It will be demonstrated that rationalizing the data along these lines leads to a consistency with the theory while relaxing some of the conceptual problems encountered in previous interpretations. The data supports the idea that the relaxation in restricting geometries proceeds like in the bulk liquid until the length scale ξ(t)αlog(t) of cooperativity reaches the pore size leading to nonergodic behavior within the experimental time scale. For a characteristic cooperativity length 4 the data analysis yields ξc(T)αT and ξc(T)≈3 nm. The solvation dynamics results under study are compared to analogous dielectric relaxation data.

Original languageEnglish (US)
Pages (from-to)15762-15766
Number of pages5
JournalPhysical Review B - Condensed Matter and Materials Physics
Volume54
Issue number22
StatePublished - Dec 1 1996
Externally publishedYes

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Solvation
solvation
Dielectric relaxation
Liquids
liquids
Pore size
Sol-gels
Molecular dynamics
Glass
Geometry
gels
molecular dynamics
porosity
glass
geometry

ASJC Scopus subject areas

  • Condensed Matter Physics

Cite this

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abstract = "The molecular dynamics of supercooled liquids confined to the mesopores of sol-gel glasses are interpreted in terms of the spatial competition between the average length scale of cooperativity assumed to increase with time and the geometrical confinement on scales between 2.5 and 7.5 nm. Opposed to relating the fast and slow relaxation components to spatially distinct regimes, the picture of a mesoscopically uniform but cooperative relaxation as stimulated by the theoretical work of J{\"a}ckle is proposed. It will be demonstrated that rationalizing the data along these lines leads to a consistency with the theory while relaxing some of the conceptual problems encountered in previous interpretations. The data supports the idea that the relaxation in restricting geometries proceeds like in the bulk liquid until the length scale ξ(t)αlog(t) of cooperativity reaches the pore size leading to nonergodic behavior within the experimental time scale. For a characteristic cooperativity length 4 the data analysis yields ξc(T)αT and ξc(T)≈3 nm. The solvation dynamics results under study are compared to analogous dielectric relaxation data.",
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