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Small Particle Driven Chain Disentanglements in Polymer Nanocomposites
Erkan Senses1,2, Siyam M Ansar3, Christopher L Kitchens3
1NIST Center for Neutron Research, National Institute of Standards and Technology, Gaithersburg, Maryland 20899-8562, USA.
Physical Review Letters
|April 22, 2017
Summary
Adding small nanoparticles to polymer composites increases the tube diameter, affecting polymer chain dynamics. Larger nanoparticles do not alter this, offering insights into nanocomposite viscosity.
Area of Science:
- Materials Science
- Polymer Physics
- Nanotechnology
Background:
- Polymer nanocomposites exhibit complex rheological behaviors.
- Understanding polymer chain dynamics and particle interactions is crucial for material design.
Purpose of the Study:
- To investigate the impact of nanoparticle size on polymer chain dynamics, particle mobility, and bulk viscosity.
- To elucidate the mechanisms behind non-Einstein-like viscosity trends in polymer nanocomposites.
Main Methods:
- Neutron spin-echo spectroscopy
- X-ray photon correlation spectroscopy
- Bulk rheology
Main Results:
- Nanoparticles smaller than the entanglement mesh size (≈5 nm) increased the reptation tube diameter by ≈25% at 20% volume fraction.
- Larger nanoparticles (20 nm) did not change the tube diameter.
- Rouse dynamics remained insensitive to particle size in both cases.
Conclusions:
- Particle size significantly influences polymer chain dynamics and rheology in nanocomposites.
- Smaller nanoparticles induce polymer disentanglement, explaining non-Einstein-like viscosity.
- This study provides direct experimental evidence for particle-size-driven rheological effects.