title: Microscopic Chain Motion in Polymer Nanocomposites with Dynamically Asymmetric Interphases.
abstract: Dynamics of the interphase region between matrix and bound polymers on nanoparticles is important to understand the macroscopic rheological properties of nanocomposites. Here, we present neutron scattering investigations on nanocomposites with dynamically asymmetric interphases formed by a high-glass transition temperature polymer, poly(methyl methacrylate), adsorbed on nanoparticles and a low-glass transition temperature miscible matrix, poly(ethylene oxide). By taking advantage of selective isotope labeling of the chains, we studied the role of interfacial polymer on segmental and collective dynamics of the matrix chains from subnanoseconds to 100 nanoseconds. Our results show that the Rouse relaxation remains unchanged in a weakly attractive composite system while the dynamics significantly slows down in a strongly attractive composite. More importantly, the chains disentangle with a remarkable increase of the reptation tube size when the bound polymer is vitreous. The glassy and rubbery states of the bound polymer as temperature changes underpin the macroscopic stiffening of nanocomposites.
authors.affiliation: NIST Center for Neutron Research, National Institute of Standards and Technology Gaithersburg, MD 20899-8562, USA.|Department of Materials Science and Engineering, University of Maryland, College Park, MD 20742-2115, USA.
authors.forename: Erkan
authors.initials: E
authors.lastname: Senses
authors.affiliation: NIST Center for Neutron Research, National Institute of Standards and Technology Gaithersburg, MD 20899-8562, USA.
authors.forename: Antonio
authors.initials: A
authors.lastname: Faraone
authors.affiliation: Department of Chemical Engineering and Materials Science, Stevens Institute of Technology, Castle Point on Hudson, Hoboken, NJ 07030-5942.
authors.forename: Pinar
authors.initials: P
authors.lastname: Akcora