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Lamellar phase separation in a centrifugal field. A method for measuring interbilayer forces

Bulut, Sanja LU ; Åslund, Ingrid LU ; Topgaard, Daniel LU ; Wennerström, Håkan LU and Olsson, Ulf LU (2010) In Soft Matter 6(18). p.4520-4527
Abstract
We present a novel method for measuring interbilayer forces in lamellar liquid crystals of amphiphile-water systems. In a centrifuge the gravitational effect is easily strong enough to produce clearly observable concentration gradients. During the experiment the concentration profile in the test-tube is monitored using NMR imaging of the deuterium quadrupole splitting in the lamellar phase, by temporarily transferring the sample into a NMR spectrometer. We also present a theoretical analysis of the experiment, where interactions dominate over entropy of mixing effects. For a system at sedimentation equilibrium one obtains a direct measurement of the interbilayer force, or equivalently chemical potential of the components over a substantial... (More)
We present a novel method for measuring interbilayer forces in lamellar liquid crystals of amphiphile-water systems. In a centrifuge the gravitational effect is easily strong enough to produce clearly observable concentration gradients. During the experiment the concentration profile in the test-tube is monitored using NMR imaging of the deuterium quadrupole splitting in the lamellar phase, by temporarily transferring the sample into a NMR spectrometer. We also present a theoretical analysis of the experiment, where interactions dominate over entropy of mixing effects. For a system at sedimentation equilibrium one obtains a direct measurement of the interbilayer force, or equivalently chemical potential of the components over a substantial concentration range. It requires long times to obtain equilibrium in the centrifuge but very useful information about equilibrium and dynamic parameters is also obtained through an analysis of the sedimentation process. Experiments were performed on samples of a dilute lamellar phase of the non-ionic surfactant C10E3. After a few days of centrifugation a consistent concentration pattern was observed. At the bottom of the sample there appears a pure water-phase. The concentration profiles stabilize after a long centrifugation time. If they are related to the phase boundary the different profiles superimpose. This observation is consistent with the theory and the observation allows for a determination of how the chemical potentials vary with composition. The observed profiles are consistent with a dominating undulation force with a bilayer bending rigidity of 4.8-5.1 kT. (Less)
Please use this url to cite or link to this publication:
author
organization
publishing date
type
Contribution to journal
publication status
published
subject
in
Soft Matter
volume
6
issue
18
pages
4520 - 4527
publisher
Royal Society of Chemistry
external identifiers
  • wos:000281613700032
  • scopus:79951609321
ISSN
1744-6848
DOI
10.1039/c0sm00085j
language
English
LU publication?
yes
id
c5cc7f5d-3f1e-4f02-8b26-ed27ab11a36e (old id 1697623)
date added to LUP
2010-10-22 12:56:18
date last changed
2018-05-29 10:23:10
@article{c5cc7f5d-3f1e-4f02-8b26-ed27ab11a36e,
  abstract     = {We present a novel method for measuring interbilayer forces in lamellar liquid crystals of amphiphile-water systems. In a centrifuge the gravitational effect is easily strong enough to produce clearly observable concentration gradients. During the experiment the concentration profile in the test-tube is monitored using NMR imaging of the deuterium quadrupole splitting in the lamellar phase, by temporarily transferring the sample into a NMR spectrometer. We also present a theoretical analysis of the experiment, where interactions dominate over entropy of mixing effects. For a system at sedimentation equilibrium one obtains a direct measurement of the interbilayer force, or equivalently chemical potential of the components over a substantial concentration range. It requires long times to obtain equilibrium in the centrifuge but very useful information about equilibrium and dynamic parameters is also obtained through an analysis of the sedimentation process. Experiments were performed on samples of a dilute lamellar phase of the non-ionic surfactant C10E3. After a few days of centrifugation a consistent concentration pattern was observed. At the bottom of the sample there appears a pure water-phase. The concentration profiles stabilize after a long centrifugation time. If they are related to the phase boundary the different profiles superimpose. This observation is consistent with the theory and the observation allows for a determination of how the chemical potentials vary with composition. The observed profiles are consistent with a dominating undulation force with a bilayer bending rigidity of 4.8-5.1 kT.},
  author       = {Bulut, Sanja and Åslund, Ingrid and Topgaard, Daniel and Wennerström, Håkan and Olsson, Ulf},
  issn         = {1744-6848},
  language     = {eng},
  number       = {18},
  pages        = {4520--4527},
  publisher    = {Royal Society of Chemistry},
  series       = {Soft Matter},
  title        = {Lamellar phase separation in a centrifugal field. A method for measuring interbilayer forces},
  url          = {http://dx.doi.org/10.1039/c0sm00085j},
  volume       = {6},
  year         = {2010},
}