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Shear-induced topology changes in liquid crystals of the soybean lecithin/DDAB/water system

Montalvo, Gemma LU ; Valiente, Mercedes and Khan, Ali LU (2007) In Langmuir 23(21). p.10518-10524
Abstract
The viscoelastic behavior of the two different liquid crystalline lamellar phases and the liquid crystalline cubic phase of the mixed soybean lecithin/DDAB system in water was studied through rheology, with mechanical parameters studied as a function of composition. The swollen or diluted lamellar region is formed by vesicles, and its characteristic flow curve presents two-power law regions separated by a region where viscosity passes through a maximum. Yield stress and shear-dependent flow behavior were also observed. The microstructure suffers transformation under shear stress, and rheological response shifts from thixotropic to antithixotropic loops. Similar theological behavior has been observed for samples in the collapsed or... (More)
The viscoelastic behavior of the two different liquid crystalline lamellar phases and the liquid crystalline cubic phase of the mixed soybean lecithin/DDAB system in water was studied through rheology, with mechanical parameters studied as a function of composition. The swollen or diluted lamellar region is formed by vesicles, and its characteristic flow curve presents two-power law regions separated by a region where viscosity passes through a maximum. Yield stress and shear-dependent flow behavior were also observed. The microstructure suffers transformation under shear stress, and rheological response shifts from thixotropic to antithixotropic loops. Similar theological behavior has been observed for samples in the collapsed or concentrated lamellar region, at the water-rich corner of the phase diagram. Vesicle formation may therefore occur by shearing the initial stacked and open bilayers. However, concentrated lamellar samples in the water-poor part of the phase diagram are less sensitive to shear effects and show plastic behavior and thixotropy. All lamellar samples manifest high elasticity. The dynamic responses of both lamellar topologies, i.e., vesicles and open bilayers, are comparable and exhibit an infinite relation time. The bicontinuous cubic, liquid crystalline phase is highly viscous. Its dynamic response cannot be modeled by a Maxwell model. (Less)
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author
organization
publishing date
type
Contribution to journal
publication status
published
subject
in
Langmuir
volume
23
issue
21
pages
10518 - 10524
publisher
The American Chemical Society
external identifiers
  • wos:000249948700016
  • scopus:35448938084
ISSN
0743-7463
DOI
10.1021/la701539f
language
English
LU publication?
yes
id
28837033-6bb3-4d69-9782-f31ad67d5038 (old id 655173)
date added to LUP
2007-12-14 13:29:58
date last changed
2017-06-11 03:38:44
@article{28837033-6bb3-4d69-9782-f31ad67d5038,
  abstract     = {The viscoelastic behavior of the two different liquid crystalline lamellar phases and the liquid crystalline cubic phase of the mixed soybean lecithin/DDAB system in water was studied through rheology, with mechanical parameters studied as a function of composition. The swollen or diluted lamellar region is formed by vesicles, and its characteristic flow curve presents two-power law regions separated by a region where viscosity passes through a maximum. Yield stress and shear-dependent flow behavior were also observed. The microstructure suffers transformation under shear stress, and rheological response shifts from thixotropic to antithixotropic loops. Similar theological behavior has been observed for samples in the collapsed or concentrated lamellar region, at the water-rich corner of the phase diagram. Vesicle formation may therefore occur by shearing the initial stacked and open bilayers. However, concentrated lamellar samples in the water-poor part of the phase diagram are less sensitive to shear effects and show plastic behavior and thixotropy. All lamellar samples manifest high elasticity. The dynamic responses of both lamellar topologies, i.e., vesicles and open bilayers, are comparable and exhibit an infinite relation time. The bicontinuous cubic, liquid crystalline phase is highly viscous. Its dynamic response cannot be modeled by a Maxwell model.},
  author       = {Montalvo, Gemma and Valiente, Mercedes and Khan, Ali},
  issn         = {0743-7463},
  language     = {eng},
  number       = {21},
  pages        = {10518--10524},
  publisher    = {The American Chemical Society},
  series       = {Langmuir},
  title        = {Shear-induced topology changes in liquid crystals of the soybean lecithin/DDAB/water system},
  url          = {http://dx.doi.org/10.1021/la701539f},
  volume       = {23},
  year         = {2007},
}