Zooming in on the role of surfactants in droplet coalescence at the macroscale and microscale. (December 2020)

• Record Type: Journal Article
• Authors: Narayan, Shweta; Metaxas, Athena E.; Bachnak, Rana; Neumiller, Thomas; Dutcher, Cari S.
• Is Part Of: Current opinion in colloid & interface science. Volume 50(2020)
• Publication Date: 2020-12
• Subjects: Surfactants -- Thin films -- Droplets -- Coalescence -- Interfacial rheology; Surface chemistry -- Periodicals; Colloids -- Periodicals; 541.33
• DOI: 10.1016/j.cocis.2020.08.010
• Languages: English
• ISSNs: 1359-0294

Abstract

Abstract: Coalescence of dispersed micrometer-scale droplets is an essential step toward the separation of emulsions. The thin film between droplets must form, drain, and rupture for coalescence to occur. In surfactant-stabilized emulsions, the film drainage and droplet coalescence processes are known to be hindered because of reduced interfacial mobility. However, a clear correlation between this mobility and the underlying surfactant transport and interfacial response to shear and dilatational deformations is undercharacterized. For microscale droplets, the effect of surfactant transport to the interface and along the interface is often difficult to isolate from other bulk effects on emulsion stability. In this work, we review surfactant-mitigated coalescence in both macroscale and microscale experiments, highlighting the importance of interfacial curvature and length scales when establishing a correlation between coalescence theory and film mobility. Graphical abstract: Image 1 Highlights: Coalescence of dispersed droplets is critical to emulsion stability and liquid–liquid separation. Role of surfactant and interfacial transport in emulsion stabilization is not fully understood. Relative importance of Marangoni effects may be different on the macroscale and microscale. Microscale studies of coalescence and interfacial rheology can inform overall emulsion stability.