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Synthesis of Cyclic Polymers and Characterization of Their Diffusive Motion in the Melt State at the Single Molecule Level
Published on: September 26, 2016
Rheological evidence for a dynamical crossover in polymer melts via nonequilibrium molecular dynamics
1Institut fur Theoretische Physik, Technische Universitat Berlin, Hardenbergstrasse 36, D-10623 Berlin, Germany and Polymer Physics, Institute of Polymers, ML H 18, ETH Zurich, CH-8092 Zurich, Switzerland.
Physical Review Letters
|September 16, 2000
Summary
A critical molecular weight governs polymer melt rheology, with a crossover observed at 100 beads per chain. This finding supports new theories on molecular weight, length, and flexibility relationships in polymer chains.
Area of Science:
- Polymer Physics
- Rheology
- Materials Science
Background:
- The rheological properties of polymer melts are significantly influenced by molecular weight.
- Understanding the relationship between molecular architecture and macroscopic behavior is crucial for polymer science.
Purpose of the Study:
- To identify the critical molecular weight controlling rheological properties in the multibead finitely extensible nonlinear elastic (FENE) chain model.
- To investigate the rheological crossover phenomenon and its relation to polymer chain characteristics.
Main Methods:
- Utilizing the multibead finitely extensible nonlinear elastic (FENE) chain model to simulate polymer melt behavior.
- Analyzing the power law behavior of viscous properties to identify rheological crossovers.
- Determining the critical number of beads per chain (N(c)) associated with rheological changes.
Main Results:
- A critical molecular weight was identified, controlling the rheological properties of the FENE chain model polymer melt.
- A rheological crossover was observed at a critical number of beads per chain, N(c) = 100 ± 10.
- A new relationship between dimensionless critical weight, characteristic length, and flexibility was confirmed.
- Entanglement molecular weight (N(e)) for flexible FENE chains may be comparable to or exceed the critical molecular weight (N(c)).
Conclusions:
- The study establishes a critical molecular weight threshold that dictates polymer melt rheology.
- The findings validate theoretical predictions linking molecular weight, chain dimensions, and flexibility.
- The entanglement molecular weight in flexible FENE models warrants further investigation in relation to critical molecular weight.
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