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Visualization of Surfactant Dynamics to and along Oil–Water Interfaces Using Solvatochromic Fluorescent Surfactants
journal contribution
posted on 2018-08-03, 00:00 authored by Christopher
V. H.-H. Chen, Ying Liu, Howard A. Stone, Robert K. Prud’hommeAlthough
many theories exist to understand the transport of surfactants
to and along interfaces under flow, few techniques are available to
directly monitor surfactant dynamics at interfaces. Due to the broad
use of surfactants, from oil spill remediation to healthcare and household
products, a better means of assessing surfactant dynamics would be
widely applicable. Here, we describe and demonstrate the use of fluorescent
surfactant-dyes as a means of dynamic visualization of surfactant
transport and have synthesized Nile Red/polyethylene glycol (NR-PEG)
derivatives for this purpose. These NR-PEG surfactant-dyes fluoresce
differently at oil–water interfaces than in bulk aqueous solution,
allowing for the selective monitoring of bound and free surfactant
using confocal microscopy. We have visualized the transport of surfactants
to and along interfaces of droplets in a pipe flow and at the interfaces
of liquid-infused surfaces undergoing shear-driven drainage. Imaging
surfactant adsorption to interfaces at these time scales will allow
for the development of improved dispersant systems for applications
such as oil spill remediation and can also be used in understanding
other fundamental transport phenomena involving dispersants.