title: Unexpected Molecular Weight Effect in Polymer Nanocomposites.
abstract: 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.
authors: Chemical Sciences Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA.
authors: Shiwang
authors: S
authors: Cheng
authors: Department of Physics and Astronomy, University of Tennessee, Knoxville, Tennessee 37996, USA.
authors: Adam P
authors: AP
authors: Holt
authors: Department of Chemistry, University of Tennessee, Knoxville, Tennessee 37996, USA.
authors: Huiqun
authors: H
authors: Wang
authors: Department of Chemistry, University of Tennessee, Knoxville, Tennessee 37996, USA.
authors: Fei
authors: F
authors: Fan
authors: Chemical Sciences Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA.
authors: Vera
authors: V
authors: Bocharova
authors: Department of Chemistry, University of Tennessee, Knoxville, Tennessee 37996, USA.
authors: Halie
authors: H
authors: Martin
authors: Department of Chemistry, University of Tennessee, Knoxville, Tennessee 37996, USA.
authors: Thusitha
authors: T
authors: Etampawala
authors: Chemical Sciences Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA.
authors: B Tyler
authors: BT
authors: White
authors: Chemical Sciences Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA.
authors: Tomonori
authors: T
authors: Saito
authors: Department of Chemistry, University of Tennessee, Knoxville, Tennessee 37996, USA.
authors: Nam-Goo
authors: NG
authors: Kang
authors: Department of Chemistry, University of Tennessee, Knoxville, Tennessee 37996, USA.
authors: Mark D
authors: MD
authors: Dadmun
authors: Department of Chemistry, University of Tennessee, Knoxville, Tennessee 37996, USA.
authors: Jimmy W
authors: JW
authors: Mays
authors: Chemical Sciences Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA.|Department of Physics and Astronomy, University of Tennessee, Knoxville, Tennessee 37996, USA.|Department of Chemistry, University of Tennessee, Knoxville, Tennessee 37996, USA.
authors: Alexei P
authors: AP
authors: Sokolov