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Kim, So Youn
Laboratory for Soft Materials Nanophysics
Research Interests
  • Colloids, particle dispersions, polymer nanocomposite, block copolymers

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Polymer Dynamics in PEG-Silica Nanocomposites: Effects of Polymer Molecular Weight, Temperature and Solvent Dilution

Cited 18 times inthomson ciCited 16 times inthomson ci
Title
Polymer Dynamics in PEG-Silica Nanocomposites: Effects of Polymer Molecular Weight, Temperature and Solvent Dilution
Other Titles
Polymer Dynamics in PEG-Silica Nanocomposites: Effects of Polymer Molecular Weight, Temperature and Solvent Dilution
Author
Kim, So YounMeyer, Henriette W.Saalwaechter, KayZukoski, Charles F.
Keywords
HYDROXYL GROUP CONTENT; MULTIPLE-QUANTUM NMR; SOLID-STATE NMR; GLASS-TRANSITION; SURFACE INTERACTIONS; CHAIN DYNAMICS; SPIN-DIFFUSION; BEHAVIOR; SPECTROSCOPY; WATER
Issue Date
2012-05
Publisher
AMER CHEMICAL SOC
Citation
MACROMOLECULES, v.45, no.10, pp.4225 - 4237
Abstract
The mechanical properties of particulate nanocomposites strongly depend upon the particle dispersion, as well as on the closely related properties in thin polymer films covering the particle surface. The length scale of such changes is relevant for the understanding of particle-particle interactions, which ultimately dominate the mechanical response. Using well-defined 44 nm diameter silica nanoparticles dispersed in poly(ethylene glycol), we focus on surface-induced changes in polymer dynamics. Using proton time-domain NMR, we distinguish three polymer phases of different mobility, i.e., a strongly adsorbed, solid-like fraction, a fraction with intermediate relaxation times and a highly mobile fraction. We explore how these fractions change as we vary polymer molecular weight from 300 to 20 000 and particle volume fraction up to 0.3. A multiple-quantum experiment enables a closer analysis of the mobile component which we show consists of two fractions, one resembling the bulk melt-like and another one showing network-like properties. We demonstrate that above a polymer molecular weight-dependent volume fraction, polymers form elastically active links between particles, resulting in the physical gelation observed in such systems. Our results provide a quantitative picture of network formation, which is described by the amount and length of network-like chains as well as heterogeneities in the polymer dynamics. We relate changes in polymer dynamics to particle microstructure obtained from small angle neutron scattering
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DOI
10.1021/ma300439k
ISSN
0024-9297
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ECHE_Journal Papers
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