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Mechanism of Spontaneous Blebbing Motion of an Oil–Water Interface: Elastic Stress Generated by a Lamellar–Lamellar Transition
journal contribution
posted on 2016-03-03, 00:00 authored by Yutaka Sumino, Norifumi L. Yamada, Michihiro Nagao, Takuya Honda, Hiroyuki Kitahata, Yuri B. Melnichenko, Hideki SetoA quaternary system composed of surfactant,
cosurfactant, oil,
and water showing spontaneous motion of the oil–water interface
under far-from-equilibrium condition is studied in order to understand
nanometer-scale structures and their roles in spontaneous motion.
The interfacial motion is characterized by the repetitive extension
and retraction of spherical protrusions at the interface, i.e, blebbing
motion. During the blebbing motion, elastic aggregates are accumulated,
which were characterized as surfactant lamellar structures with mean
repeat distances d of 25 to 40 nm. Still unclear
is the relationship between
the structure formation and the dynamics of the interfacial motion.
In the present study, we find that a new lamellar structure with d larger than 80 nm is formed at the blebbing oil–water
interface, while the resultant elastic aggregates, which are the one
reported before, have a lamellar structure with smaller d (25 to 40 nm). Such transition of lamellar structures from the larger d to smaller d is induced by a penetration
of surfactants from an aqueous phase into the aggregates. We propose
a model in which elastic stress generated by the transition drives
the blebbing motion at the interface. The present results explain
the link between nanometer-scale transition of lamellar structure
and millimeter-scale dynamics at an oil–water interface.