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Simulation of phase equilibria in lamellar surfactant systems

Turesson, Martin LU ; Forsman, Jan LU ; Åkesson, Torbjörn LU and Jönsson, Bo LU (2004) In Langmuir 20(12). p.5123-5126
Abstract
The coexistence of two lamellar liquid crystalline phases has been investigated by means of Monte Carlo simulations. The surfaces of the negatively charged bilayers formed by the surfactant molecules are modeled as planar infinite walls with a uniform surface charge density. Water is treated as a dielectric continuum, and only electrostatic interactions are considered. The counterions are mono- and divalent point ions, and their ratio is allowed to vary. Monovalent counterions lead to a repulsive osmotic pressure at all separations, while an attractive region exists when the counterions are divalent. In the latter case, one would expect a phase separation to take place, although it is not observed experimentally due to the limited... (More)
The coexistence of two lamellar liquid crystalline phases has been investigated by means of Monte Carlo simulations. The surfaces of the negatively charged bilayers formed by the surfactant molecules are modeled as planar infinite walls with a uniform surface charge density. Water is treated as a dielectric continuum, and only electrostatic interactions are considered. The counterions are mono- and divalent point ions, and their ratio is allowed to vary. Monovalent counterions lead to a repulsive osmotic pressure at all separations, while an attractive region exists when the counterions are divalent. In the latter case, one would expect a phase separation to take place, although it is not observed experimentally due to the limited stability of the lamellar phase at high water content. In a system with mixed counterions, however, the osmotic pressure exhibits a van der Waals loop under such conditions that two phases can coexist. A phase diagram is constructed, and the agreement with experimental data is excellent. (Less)
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author
organization
publishing date
type
Contribution to journal
publication status
published
subject
in
Langmuir
volume
20
issue
12
pages
5123 - 5126
publisher
The American Chemical Society
external identifiers
  • wos:000221846000050
  • pmid:15984278
  • scopus:2942733694
ISSN
0743-7463
DOI
10.1021/la049858i
language
English
LU publication?
yes
id
2e391ff9-d135-432b-8109-3bc2a3c286b9 (old id 139657)
date added to LUP
2007-07-17 14:15:41
date last changed
2017-07-02 03:34:51
@article{2e391ff9-d135-432b-8109-3bc2a3c286b9,
  abstract     = {The coexistence of two lamellar liquid crystalline phases has been investigated by means of Monte Carlo simulations. The surfaces of the negatively charged bilayers formed by the surfactant molecules are modeled as planar infinite walls with a uniform surface charge density. Water is treated as a dielectric continuum, and only electrostatic interactions are considered. The counterions are mono- and divalent point ions, and their ratio is allowed to vary. Monovalent counterions lead to a repulsive osmotic pressure at all separations, while an attractive region exists when the counterions are divalent. In the latter case, one would expect a phase separation to take place, although it is not observed experimentally due to the limited stability of the lamellar phase at high water content. In a system with mixed counterions, however, the osmotic pressure exhibits a van der Waals loop under such conditions that two phases can coexist. A phase diagram is constructed, and the agreement with experimental data is excellent.},
  author       = {Turesson, Martin and Forsman, Jan and Åkesson, Torbjörn and Jönsson, Bo},
  issn         = {0743-7463},
  language     = {eng},
  number       = {12},
  pages        = {5123--5126},
  publisher    = {The American Chemical Society},
  series       = {Langmuir},
  title        = {Simulation of phase equilibria in lamellar surfactant systems},
  url          = {http://dx.doi.org/10.1021/la049858i},
  volume       = {20},
  year         = {2004},
}