Products Cited in Publications Worldwide Liquid-liquid surfactant partitioning drives dewetting of oil from hydrophobic surfaces

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

Kueyoung E. Kim; Wangyang Xue; Lauren D. Zarzar

DOI:

Abstract

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 oils as well as aromatic oils and focus on common nonionic nonylphenol ethoxylate . 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.

Keywords

Wetting ; Surfactant ; Adsorption ; Partitioning ; Sessile Droplet

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A15888216415-12-695%

Hexadecyltrimethoxysilane

61.0/1kg

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