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The dynamics of single chains within a model polymer melt.
Julie A McCormick1, Carol K Hall, Saad A Khan
1Department of Chemical and Biomolecular Engineering, North Carolina State University, Raleigh, 27695-7905, USA.
The Journal of Chemical Physics
|April 20, 2005
Summary
Localized entanglements significantly impact polymer melt dynamics. Individual polymer chains show diverse behaviors, including superdiffusion and anomalous relaxation, indicating these effects are single-chain properties.
Area of Science:
- Polymer Physics
- Computational Materials Science
Background:
- Entangled polymer melts exhibit complex dynamics.
- Previous studies suggested anomalous relaxation-memory-release behavior.
Purpose of the Study:
- To investigate the effect of localized entanglements on individual chain dynamics in polymer melts.
- To determine if anomalous relaxation is a single-chain phenomenon.
Main Methods:
- Discontinuous molecular dynamics simulations were used.
- Simulations involved 32 hard chains (length 192) at phi = 0.45.
- Analysis included mean squared displacements, diffusion coefficients, and end-to-end vector autocorrelation functions.
Main Results:
- Individual chains displayed a wide distribution of diffusive behaviors (superdiffusive, diffusive, subdiffusive).
- End-to-end vector autocorrelation functions showed significant variation in relaxation times, with nearly half exhibiting anomalous behavior.
- Anomalous relaxation-memory-release behavior was confirmed as a single-chain property.
Conclusions:
- Localized entanglements create heterogeneous dynamics within polymer melts.
- Individual chain behavior deviates significantly from the system average.
- Anomalous dynamics are intrinsic to specific chains, not just system-wide effects.