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Unexpected Molecular Weight Effect in Polymer Nanocomposites.
Shiwang Cheng1, Adam P Holt2, Huiqun Wang3
1Chemical Sciences Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA.
Physical Review Letters
|February 6, 2016
Summary
The interfacial layer in polymer nanocomposites (PNCs) shows unexpected behavior. Its thickness with hindered relaxation decreases as polymer molecular weight increases, challenging current theories.
Area of Science:
- Materials Science
- Polymer Science
- Nanotechnology
Background:
- The interfacial layer in polymer nanocomposites (PNCs) critically influences macroscopic properties.
- While static interfacial layer thickness increases with molecular weight (MW), its dynamic behavior and glass transition effects are less understood.
Purpose of the Study:
- To investigate the influence of polymer molecular weight (MW) on segmental relaxation and glass transition within the interfacial layer of PNCs.
- To explore the relationship between MW, interfacial layer dynamics, and mass density in PNCs with attractive polymer-nanoparticle interactions.
Main Methods:
- Analysis of interfacial layer properties in polymer nanocomposites.
- Investigating the dependence of segmental relaxation and glass transition on polymer molecular weight.
- Characterization of mass density within the interfacial layer.
Main Results:
- An unexpected decrease in the thickness of the interfacial layer with hindered segmental relaxation as MW increases.
- This finding contrasts sharply with existing theoretical predictions.
- A reduction in the mass density of the interfacial layer was observed with increasing MW.
Conclusions:
- The study reveals a novel, counterintuitive dependence of interfacial layer dynamics on MW in PNCs.
- Observed effects challenge current models of polymer nanocomposite behavior.
- Findings suggest new strategies for tailoring PNC properties by controlling MW and interfacial characteristics.
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