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Linlin Chu1, Kaipin Xu2, Robert Graf3

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Chain entanglement in Poly(ethylene oxide) (PEO) melts begins around 6 kg/mol. Higher molecular weights show distinct entanglement dynamics, influenced by chain mobility and heterogeneity.

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Area of Science:

  • Polymer Physics
  • Materials Science

Background:

  • Polymer chain entanglement is crucial for material properties.
  • Understanding entanglement dynamics is key to predicting polymer behavior.

Purpose of the Study:

  • To investigate chain entanglement behaviors in Poly(ethylene oxide) (PEO) melts.
  • To determine the critical molecular weight for PEO entanglement.
  • To explore the impact of molecular weight on entanglement dynamics and heterogeneity.

Main Methods:

  • Utilized 1H Hahn echo nuclear magnetic resonance (NMR) experiments.
  • Employed 1H double-quantum (DQ) NMR spectroscopy.
  • Studied PEO melts with varying molecular weights (2, 255, and 480 kg/mol).

Main Results:

  • Identified a critical molecular weight of approximately 6 kg/mol for PEO entanglement.
  • Observed anisotropic chain motion above the critical molecular weight.
  • PEO melts above the critical molecular weight exhibit dynamical entanglements.
  • Higher molecular weight PEO (PEO480) showed slow mobility and homogeneous entanglements.
  • Lower molecular weight PEO (PEO255) displayed fast mobility and heterogeneous entanglements.
  • Short PEO chains acted as solvents, increasing chain mobility and inducing heterogeneity in PEO480.

Conclusions:

  • Chain entanglement in PEO melts is molecular weight-dependent.
  • Dynamical entanglements significantly influence polymer chain mobility and distribution.
  • Short PEO chains can effectively modify the entanglement network and dynamics of longer chains.