Unexpected Molecular Weight Effect in Polymer Nanocomposites

The properties of the interfacial layer between the polymer matrix and nanoparticles largely determine the macroscopic properties of polymer nanocomposites (PNCs). Although the static thickness of the interfacial layer was found to increase with the molecular weight (MW), the influence of MW on segm...

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Bibliographic Details
Published in:Physical review letters 2016-01, Vol.116 (3), p.038302-038302, Article 038302
Main Authors: Cheng, Shiwang, Holt, Adam P, Wang, Huiqun, Fan, Fei, Bocharova, Vera, Martin, Halie, Etampawala, Thusitha, White, B Tyler, Saito, Tomonori, Kang, Nam-Goo, Dadmun, Mark D, Mays, Jimmy W, Sokolov, Alexei P
Format: Article
Language:English
Subjects:
Density
Dynamic tests
Dynamics
Glass transition
Interfacial properties
MATERIALS SCIENCE
Molecular weight
Nanocomposites
Nanoparticles
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Summary:The properties of the interfacial layer between the polymer matrix and nanoparticles largely determine the macroscopic properties of polymer nanocomposites (PNCs). Although the static thickness of the interfacial layer was found to increase with the molecular weight (MW), the influence of MW on segmental relaxation and the glass transition in this layer remains to be explored. In this Letter, we show an unexpected MW dependence of the interfacial properties in PNC with attractive polymer-nanoparticle interactions: the thickness of the interfacial layer with hindered segmental relaxation decreases as MW increases, in sharp contrast to theoretical predictions. Further analyses reveal a reduction in mass density of the interfacial layer with increasing MW, which can elucidate these unexpected dynamic effects. Our observations call for a significant revision of the current understandings of PNCs and suggest interesting ways to tailor their properties.
ISSN:0031-9007
1079-7114
DOI:10.1103/PhysRevLett.116.038302