Shear-induced sponge-to-lamellar transition in bicontinuous microemulsions evidenced by microfluidic-SANS
File(s)
Author(s)
Fischer, Julian
Porcar, Lionel
Cabral, Joao T
Sottmann, Thomas
Type
Journal Article
Abstract
Hypothesis
Shear flow applied to bicontinuous microemulsions is expected to induce a transition to lamellae via the suppression of surfactant monolayer fluctuations. Compared to the topologically analogous
(sponge) phase, composed of surfactant bilayers, this transition is likely to occur at much higher shear rates.
Experiments
We examine the flow response of a model bicontinuous microemulsion, D2O/n-octane/C10E4 by coupling microfluidics with small-angle neutron scattering (SANS), attaining wall shear rates in excess of 105 s−1. The reduction of probed sample volumes down to
10 nL allows the spatial mapping of the structural and orientation changes within the microchannel, as a function of the flow field components.
Findings
With increasing flow rate, we observe a gradual increase in scattering anisotropy, accompanied by a decrease of the microemulsion domain size along the main flow orientation. A consistent description of the degree of anisotropy was obtained when considering the velocity gradient along the scattering plane perpendicular to the flow. We discuss the flow dependence of the effective bending rigidity, rationalizing a strong influence of shear on thermal membrane fluctuations. Assuming a similar shear dependence for the saddle splay modulus, the bicontinuous-to-lamellar transition can be attributed to the gradual disappearance of inter-lamellar passages.
Shear flow applied to bicontinuous microemulsions is expected to induce a transition to lamellae via the suppression of surfactant monolayer fluctuations. Compared to the topologically analogous
(sponge) phase, composed of surfactant bilayers, this transition is likely to occur at much higher shear rates.
Experiments
We examine the flow response of a model bicontinuous microemulsion, D2O/n-octane/C10E4 by coupling microfluidics with small-angle neutron scattering (SANS), attaining wall shear rates in excess of 105 s−1. The reduction of probed sample volumes down to
10 nL allows the spatial mapping of the structural and orientation changes within the microchannel, as a function of the flow field components.
Findings
With increasing flow rate, we observe a gradual increase in scattering anisotropy, accompanied by a decrease of the microemulsion domain size along the main flow orientation. A consistent description of the degree of anisotropy was obtained when considering the velocity gradient along the scattering plane perpendicular to the flow. We discuss the flow dependence of the effective bending rigidity, rationalizing a strong influence of shear on thermal membrane fluctuations. Assuming a similar shear dependence for the saddle splay modulus, the bicontinuous-to-lamellar transition can be attributed to the gradual disappearance of inter-lamellar passages.
Date Issued
2023-04
Date Acceptance
2022-12-22
Citation
Journal of Colloid and Interface Science, 2023, 635, pp.588-597
ISSN
0021-9797
Publisher
Elsevier
Start Page
588
End Page
597
Journal / Book Title
Journal of Colloid and Interface Science
Volume
635
Copyright Statement
Copyright © Elsevier Ltd. All rights reserved. This manuscript version is made available under the CC-BY-NC-ND 4.0 license https://creativecommons.org/licenses/by-nc-nd/4.0/
Identifier
https://www.webofscience.com/api/gateway?GWVersion=2&SrcApp=PARTNER_APP&SrcAuth=LinksAMR&KeyUT=WOS:000920336000001&DestLinkType=FullRecord&DestApp=ALL_WOS&UsrCustomerID=a2bf6146997ec60c407a63945d4e92bb
Subjects
ANGLE NEUTRON-SCATTERING
Bicontinuous microemulsions
Chemistry
Chemistry, Physical
ELASTIC PROPERTIES
MEMBRANES
Microfluidics
PHASE-BEHAVIOR
Physical Sciences
RHEOLOGY
Science & Technology
Self-assembly
Shear deformation
Small-angle neutron scattering
Sponge-to-lamellar transition
Surfactant monolayers
SYSTEMS
THERMODYNAMICS
TRANSFORMATIONS
WATER
WETTING TRANSITION
Publication Status
Published
Date Publish Online
2022-12-28