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Polymer Classification: Crystallinity

Unlike ionic or small covalent molecules, polymers do not form crystalline solids due to the diffusion limitations of their long-chain structures. However, polymers contain microscopic crystalline domains separated by amorphous domains.
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Synthesis of Cyclic Polymers and Characterization of Their Diffusive Motion in the Melt State at the Single Molecule Level
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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

Time-dependent orientation coupling in equilibrium polymer melts.

Jing Cao1, Alexei E Likhtman

  • 1Department of Mathematics, University of Reading, Whiteknights, Reading RG6 6AX, United Kingdom.

Physical Review Letters
|September 28, 2010
PubMed
Summary
This summary is machine-generated.

This study introduces a new model for polymer chain motion, revealing that chains are not independent. The findings show significant orientation coupling in polymer melts, impacting their dynamics.

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Area of Science:

  • Polymer Physics
  • Materials Science
  • Computational Chemistry

Background:

  • Traditional models like Rouse and reptation assume independent polymer chain relaxation.
  • Experimental evidence contradicts this independence in concentrated polymer systems.
  • A need exists for a model that accounts for inter-chain interactions.

Purpose of the Study:

  • To propose a universal description for orientation coupling in polymer melts.
  • To introduce a time-dependent coupling parameter, κ(t), for quantifying inter-chain interactions.
  • To investigate the influence of chain length and blend composition on coupling.

Main Methods:

  • Utilized molecular dynamics simulations to model polymer melt behavior.
  • Analyzed the time evolution of the orientation coupling parameter κ(t).
  • Examined dynamics in mixtures of varying molecular weights.

Main Results:

  • Demonstrated that the coupling parameter κ(t) increases with time, reaching ~50% at long times.
  • Showed this coupling is independent of chain length and blend composition.
  • Confirmed that entanglements play a minimal role in the observed coupling.

Conclusions:

  • The proposed model provides a universal description of orientation coupling in polymer melts.
  • The findings enable predictions of component dynamics in polymer mixtures.
  • Inter-chain orientation coupling is a significant factor in polymer dynamics, even in unentangled melts.