Products Cited in Publications Worldwide Dynamic Partitioning of Surfactants in Non-Equilibrium Emulsions: Impact on Interfacial Tension, Phase Behavior, and Wetting Dynamics

Dynamic Partitioning of Surfactants in Non-Equilibrium Emulsions: Impact on Interfacial Tension, Phase Behavior, and Wetting Dynamics

Xue, Wangyang

Abstract

This dissertation investigates the dynamic partitioning of surfactants into non-equilibrium emulsions, with a focus on understanding how these processes influence interfacial tension, phase behavior, and droplet wetting dynamics. Surfactant partitioning is a critical factor in stabilizing emulsions, where surfactant molecules migrate from the continuous aqueous phase to the dispersed oil phase, altering the interfacial properties. Traditional studies often rely on bulk two-phase equilibrium partitioning tests, which fail to capture the complexities of non-equilibrium conditions found in real-world emulsions. Here, we utilize a "single-droplet extraction" method to measure surfactant partitioning into oil microdroplets, providing a detailed understanding of these dynamic processes. Our experiments focus on the partitioning behavior of Tergitol NP-9, a , into tetrachloroethylene (TCE) and other oils, examining how droplet size and surfactant concentration influence the steady-state surfactant concentration within the oil phase. We found that partitioning is more pronounced in smaller droplets, with higher surface-area-to-volume ratios driving rapid cross-interface transport of surfactants. Larger droplets take longer to reach a steady state and exhibit lower partitioning coefficients, underscoring the importance of considering droplet size in surfactant dynamics. The results also indicate that non-equilibrium processes can lead to ultra-low interfacial tension and droplet deformation over time, phenomena not accounted for by equilibrium models. Additionally, we explore how surfactant partitioning affects wetting dynamics on solid substrates, particularly the unexpected dewetting behavior of oil droplets on hydrophobic surfaces in the presence of surfactants. This behavior, influenced by surfactant adsorption and partitioning, suggests that the surface tension at both the oil-water and solid-oil interfaces is highly dynamic and responsive to surfactant concentration and distribution. The findings challenge existing models of droplet wetting and motility, offering new insights into how surfactant partitioning can be tuned to engineer responsive, self-organizing emulsions with complex functionalities. This research advances our understanding of non-equilibrium surfactant partitioning and its critical role in emulsion stability and droplet behavior. The results have broad implications for industries that rely on emulsions, including pharmaceuticals, food science, and materials engineering, where optimizing emulsion stability is essential for product performance.

Purchased from AmBeed

A15888216415-12-695%

Hexadecyltrimethoxysilane

61.0/1kg

Detail