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Static and dynamic properties of supercooled thin polymer films
F Varnik1, J Baschnagel, K Binder
1Institut für Physik, Johannes-Gutenberg Universität, D-55099 Mainz, Germany. varnik@cecam.fr
The European Physical Journal. E, Soft Matter
|March 11, 2004
Summary
Supercooled polymer melts confined in thin films exhibit bulk-like properties. Mode-coupling theory (MCT) successfully describes their dynamic and static behavior, revealing a confinement-dependent critical temperature.
Area of Science:
- Polymer Physics
- Materials Science
- Computational Chemistry
Background:
- Understanding polymer melt dynamics is crucial for material properties.
- Geometric confinement can significantly alter polymer behavior.
- Mode-coupling theory (MCT) provides a framework for analyzing relaxation dynamics.
Purpose of the Study:
- To investigate the dynamic and static properties of supercooled polymer melts under confinement.
- To compare confined polymer behavior with bulk properties and analyze using MCT.
- To explore the influence of film thickness on polymer dynamics and critical temperature.
Main Methods:
- Molecular-dynamics (MD) simulations were employed to model polymer melts.
- Simulations were conducted for systems confined between smooth, repulsive walls.
- Varying wall-to-wall separation (film thickness, D) from ~3 to ~14 times the bulk radius of gyration.
Main Results:
- Confined supercooled films showed qualitative features consistent with bulk behavior and MCT predictions.
- Observed phenomena include two-step relaxation, time-temperature superposition, and space-time factorization.
- The critical temperature T(c) of MCT decreases with decreasing film thickness D.
Conclusions:
- Geometric confinement does not fundamentally alter the qualitative dynamics of supercooled polymer melts.
- The effective critical temperature T(c) is dependent on film thickness.
- The quantity T - T(c)(D) serves as a relevant temperature scale for both bulk and confined systems.