Liquid-liquid surfactant partitioning drives dewetting of oil from hydrophobic surfaces

Hypothesis: Sessile droplets solubilizing in surfactant solution are frequently encountered in practice, but the factors governing their non-equilibrium dynamics are not well understood. Here, we investigate mechanisms by which solubilizing, sessile oil droplets in aqueous surfactant solution dewet from hydrophobic substrates and spread on hydrophilic substrates.

Experiments: We quantify the dependence of droplet contact line dynamics on drop size and oil, surfactant, and substrate chemistries. We consider halogenated alkane oils as well as aromatic oils and focus on common nonionic nonylphenol ethoxylate surfactants. We correlate these results with measurements of the interfacial tensions.

Findings: Counter-intuitively, under a range of conditions, we observe complete dewetting of oil from hydrophobic substrates but spreading on hydrophilic substrates. The timescales needed to reach a steady-state contact angle vary widely, with some droplets examined taking over a day. We find that surfactant surface adsorption governs the contact angle on shorter timescales, while partitioning of surfactant from water to oil, and oil solubilization into the water, act on longer timescales to facilitate the complete dewetting. Understanding of the role played by surfactant and oil transport presents opportunities for tailoring sessile droplet behaviors and controlling droplet dynamics under conditions that would previously not have been considered.

© This manuscript version is made available under the CC-BY-NC-ND 4.0 license https://creativecommons.org/licenses/by-nc-nd/4.0/

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Work Title Liquid-liquid surfactant partitioning drives dewetting of oil from hydrophobic surfaces
Access
Open Access
Creators
  1. Kueyoung E. Kim
  2. Wangyang Xue
  3. Lauren D. Zarzar
Keyword
  1. Wetting
  2. Surfactant
  3. Adsorption
  4. Partitioning
  5. Sessile droplet
License CC BY-NC-ND 4.0 (Attribution-NonCommercial-NoDerivatives)
Work Type Article
Publisher
  1. Journal of Colloid and Interface Science
Publication Date December 14, 2023
Publisher Identifier (DOI)
  1. https://doi.org/10.1016/j.jcis.2023.12.054
Deposited February 12, 2024

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Version 1
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  • Created
  • Added combo_with_SI.pdf
  • Added Creator Kueyoung E. Kim
  • Added Creator Wangyang Xue
  • Added Creator Lauren D. Zarzar
  • Published
  • Updated Keyword, Description, Publication Date Show Changes
    Keyword
    • Wetting, Surfactant, Adsorption, Partitioning, Sessile droplet
    Description
    • <p>Hypothesis: Sessile droplets solubilizing in surfactant solution are frequently encountered in practice, but the factors governing their non-equilibrium dynamics are not well understood. Here, we investigate mechanisms by which solubilizing, sessile oil droplets in aqueous surfactant solution dewet from hydrophobic substrates and spread on hydrophilic substrates. Experiments: We quantify the dependence of droplet contact line dynamics on drop size and oil, surfactant, and substrate chemistries. We consider halogenated alkane oils as well as aromatic oils and focus on common nonionic nonylphenol ethoxylate surfactants. We correlate these results with measurements of the interfacial tensions. Findings: Counter-intuitively, under a range of conditions, we observe complete dewetting of oil from hydrophobic substrates but spreading on hydrophilic substrates. The timescales needed to reach a steady-state contact angle vary widely, with some droplets examined taking over a day. We find that surfactant surface adsorption governs the contact angle on shorter timescales, while partitioning of surfactant from water to oil, and oil solubilization into the water, act on longer timescales to facilitate the complete dewetting. Understanding of the role played by surfactant and oil transport presents opportunities for tailoring sessile droplet behaviors and controlling droplet dynamics under conditions that would previously not have been considered.</p>
    • <p>Hypothesis: Sessile droplets solubilizing in surfactant solution are frequently encountered in practice, but the factors governing their non-equilibrium dynamics are not well understood. Here, we investigate mechanisms by which solubilizing, sessile oil droplets in aqueous surfactant solution dewet from hydrophobic substrates and spread on hydrophilic substrates.
    • Experiments: We quantify the dependence of droplet contact line dynamics on drop size and oil, surfactant, and substrate chemistries. We consider halogenated alkane oils as well as aromatic oils and focus on common nonionic nonylphenol ethoxylate surfactants. We correlate these results with measurements of the interfacial tensions.
    • Findings: Counter-intuitively, under a range of conditions, we observe complete dewetting of oil from hydrophobic substrates but spreading on hydrophilic substrates. The timescales needed to reach a steady-state contact angle vary widely, with some droplets examined taking over a day. We find that surfactant surface adsorption governs the contact angle on shorter timescales, while partitioning of surfactant from water to oil, and oil solubilization into the water, act on longer timescales to facilitate the complete dewetting. Understanding of the role played by surfactant and oil transport presents opportunities for tailoring sessile droplet behaviors and controlling droplet dynamics under conditions that would previously not have been considered.</p>
    Publication Date
    • 2024-03-15
    • 2023-12-14
  • Updated