Entropic, Electrostatic, and Interfacial Model for Osmotic Pressure and Shear Moduli of Concentrated Disordered Charged Droplets

ORAL

Abstract

We present a free energy model describing the osmotic pressure Π and the linear plateau shear moduli G'p of disordered charge-stabilized uniform emulsions for droplet volume fractions φ below, near, and above the jamming point. The three principle contributing free energy terms arise from entropy, screened-charge electrostatic interactions, and interfacial droplet deformations (EEI). We numerically evaluate Π(φ) and G'p(φ) by minimizing the total free energy with respect to a common average deformation parameter which links all three terms and taking the appropriate thermodynamic derivative. We demonstrate that this EEI model fits measurements of Π(φ) and G'p(φ) for quenched disordered nano- and micro-scale monodisperse charge-stabilized emulsions, including those having added concentrations of NaCl. In addition, trends in optical measurements of long-time plateau mean square displacements of monodisperse charge-stabilized emulsions having varying φ and concentrations of NaCl can match the trends in low-frequency G'p(φ) predicted by this EEI model. This EEI model may serve as a good starting point for understanding other disordered systems of charge-stabilized uniform spherical soft colloidal objects.

*Acknowledgements. The authors thank UCLA for financial support.

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Presenters

  • Ha Seong Kim

    • Department of Chemistry and Biochemistry, Univ of California - Los Angeles

Authors

  • Ha Seong Kim

    • Department of Chemistry and Biochemistry, Univ of California - Los Angeles

  • Frank Scheffold

    • Univ of Fribourg-Perolles
    • Physics Department, University of Fribourg
    • Physics, University of Fribourg

  • Thomas Mason

    • Department of Chemistry and Biochemistry; Department of Physics and Astronomy, University of California, Los Angeles
    • Physics & Astronomy and Chemistry & Biochemistry, UCLA
    • Department of Chemistry and Biochemistry ; Department of Physics and Astronomy, Univ of California - Los Angeles
    • Dept. of Physics & Astronomy, University of California - Los Angeles
    • Dept. of Physics and Astronomy, University of California - Los Angeles