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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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Long Wavelength Concentration Fluctuations and Cage Scale Ordering of Nanoparticles in Concentrated Polymer Solutions

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Title
Long Wavelength Concentration Fluctuations and Cage Scale Ordering of Nanoparticles in Concentrated Polymer Solutions
Other Titles
Long Wavelength Concentration Fluctuations and Cage Scale Ordering of Nanoparticles in Concentrated Polymer Solutions
Author
Kim, So YounHall, Lisa M.Schweizer, Kenneth S.Zukoski, Charles F.
Keywords
DEPLETION THEORIES; PHASE-TRANSITIONS; SILICA SURFACE; STABILITY; SUSPENSIONS; FLUIDS; NANOCOMPOSITES; STABILIZATION; DISPLACEMENT; SEPARATION
Issue Date
2010-12
Publisher
AMER CHEMICAL SOC
Citation
MACROMOLECULES, v.43, no.23, pp.10123 - 10131
Abstract
Ultrasmall-angle X-ray scattering is employed to probe the local and long wavelength collective structure of ternary mixtures of silica nanoparticles suspended in concentrated solutions of polyethyleneglycol in the good solvent ethanol. In the dilute polymer limit, these suspensions are stabilized via electrostatic repulsions, at intermediate polymer concentrations the nanoparticles aggregate, while in the polymer melt limit they again become homogeneous due to the formation of thermodynamically stable discrete adsorbed polymer layers on the nanoparticles. Solvent dilution of the polymer melt is found to modify the nanoparticle concentration fluctuations on all length scales in a manner that can be understood as a monotonic reduction of the favorable polymer particle interfacial cohesive attraction. The measurements are quantitatively compared with predictions of the two-component Polymer Reference Interaction Site Model theory modified to account in an implicit manner for solvent addition via an effective contact strength of interfacial attraction, epsilon(pc). Good agreement between theory and experiment is found without adjustable parameters based on the idea that epsilon(pc) linearly decreases with solvent volume fraction. The joint experimental-theoretical work suggests a new mechanism for restabilization of aggregated particle suspensions at high polymer concentration based on the thermodynamically controlled interface cohesion of weakly adsorbing polymers that contrasts with the classic kinetic repulsive barrier mechanism under nonadsorbing depletion attraction conditions
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DOI
10.1021/ma1021677
ISSN
0024-9297
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ECHE_Journal Papers
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