Distribution of Relaxation Dynamics in Polymer Nanocomposites: Wetting and Chain Packing Effects
ORAL
Abstract
Broadband dielectric spectroscopy and differential scanning calorimetry are used to study dynamics and glass transition temperature of poly(methyl methacrylate)/silica nanoparticle (NP) composites. By systematically examining nanocomposites based on non-functionalized SiO2 NPs dispersed in PMMA matrices and on PMMA-grafted SiO2 NPs in PMMA matrices, we probe the effects of interfacial interactions and confinement in each of these cases on segmental dynamics and Tg. In addition to slower mobility assigned to interfacial relaxations, faster modes – dependent in NP loading level and the molecular weight of the matrix – also arise due to confinement effects. These faster modes are more pronounced in nanocomposites with polymer-grafted nanoparticles. We explain these observations in a unifying way by invoking the concepts of chain wetting and packing in interfacial zones around nanofillers. As a result, these insights provide a possible molecular understanding of well-known macroscopic phenomena in polymer nanocomposites, which may inform efforts to strengthen materials or tailor the nanocomposites for specific applications.
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Presenters
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Emmanuel Mapesa
Department of Chemical and Biomolecular Engineering, University of Tennessee, Knoxville
Authors
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Emmanuel Mapesa
Department of Chemical and Biomolecular Engineering, University of Tennessee, Knoxville
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Dayton P Street
University of Tennessee, Department of Chemical and Biomolecular Engineering, University of Tennessee, Knoxville
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S. Michael Kilbey,II
Department of Chemical and Biomolecular Engineering, University of Tennessee, Knoxville
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Joshua Sangoro
Department of Chemical and Biomolecular Engineering, University of Tennessee, University of Tennessee, Department of Chemical and Biomolecular Engineering, University of Tennessee, Knoxville