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Interactions of Water Droplets in Organic Media

  • Author / Creator
    Afsaneh, Hadi
  • Emulsion droplets are present in various systems and their dynamic behaviors are important to the design of efficient processes in different biological and industrial applications. Studying the interaction mechanisms of deformable droplets provides fundamental insights into many unsolved problems in the field of droplet dynamics. Also, the properties of the thin liquid film between droplets during their interactions is of significant importance in the stability of emulsions. During the past few years, oil-in-water systems have been the center of attention in many theoretical and experimental studies due to their numerous applications, and hence, the dynamic behaviors of oil droplets inside aqueous solutions are well understood. However, water-in-oil systems are relatively new and require more studies to fully appreciate the underlying interaction mechanisms of water droplets within surrounding oil phases. Our investigations show that the Stokes–Reynolds–Young–Laplace model, as the currently established model for the study of droplet interaction in a medium, does not describe the experimental force versus piezo-displacement data for two water droplets inside a pure oil medium in the literature, and a further relatively long-ranged attractive force is required to explain these observations. In this study, we hypothesize that the source of the unexplored long-ranged force pertains to the presence of charges at the interface of the water drops with the oil phase. We propose fixed-surface-charge–bulk-dipole attraction, or charge–dipole interaction for short, as a new interaction force between water-in-oil droplets and then derive an equation for its disjoining pressure to add into the current Stokes–Reynolds–Young–Laplace model. The numerical results demonstrate that the force versus piezo-displacement curves deviate from experimental data in the literature in the absence of charge–dipole attraction while they are in excellent agreement with experimental data when charge–dipole attraction is included. Furthermore, we mathematically prove that electric double layer and surface electrostatic interactions are absent between two water droplets inside a pure organic phase as suggested by the experimental data, and therefore van der Waals and charge–dipole interactions are the only intermolecular and surface forces between water drops immersed within a pure oil medium. Our mathematical derivations show that although charges are present at the interface of water with a pure oil phase, no electrostatic interaction is present. This research indicates that charge–dipole attraction can adequately explain the unexplained attractive force observed in literature and provides a critical foundation for the study of water-in-oil emulsions with significant implications in different industries.

  • Subjects / Keywords
  • Graduation date
    Spring 2023
  • Type of Item
    Thesis
  • Degree
    Master of Science
  • DOI
    https://doi.org/10.7939/r3-0zt5-pk02
  • License
    This thesis is made available by the University of Alberta Libraries with permission of the copyright owner solely for non-commercial purposes. This thesis, or any portion thereof, may not otherwise be copied or reproduced without the written consent of the copyright owner, except to the extent permitted by Canadian copyright law.