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Impact of branching on the viscoelasticity of wormlike reverse micelles

Angelico, Ruggero; Amin, Samiul; Monduzzi, Maura; Murgia, Sergio; Olsson, Ulf LU and Palazzo, Gerardo (2012) In Soft Matter 8(42). p.10941-10949
Abstract
We present an investigation on the effect of inter-micellar connections (branches) on the rheology of wormlike micelles. The system chosen is made of lecithin, minute amounts of water and organic solvents. Lecithin and water self-assemble into wormlike reverse micelles that can be branched or unbranched depending on the oil composition (and on the water content). In this respect, cyclohexane favours disconnected reverse micelles while isooctane promotes the formation of branches. By using mixtures of cyclohexane and isooctane as the oil phase and different water/lecithin ratios, the branch density of the system can be finely tuned. PGSE-NMR experiments allowed us to distinguish between branch-free (unbranched) and branched systems and the... (More)
We present an investigation on the effect of inter-micellar connections (branches) on the rheology of wormlike micelles. The system chosen is made of lecithin, minute amounts of water and organic solvents. Lecithin and water self-assemble into wormlike reverse micelles that can be branched or unbranched depending on the oil composition (and on the water content). In this respect, cyclohexane favours disconnected reverse micelles while isooctane promotes the formation of branches. By using mixtures of cyclohexane and isooctane as the oil phase and different water/lecithin ratios, the branch density of the system can be finely tuned. PGSE-NMR experiments allowed us to distinguish between branch-free (unbranched) and branched systems and the response of the very same samples to mechanical stress was measured by rheology. This allows, for the first time, an experimental correlation between rheological properties and the presence of branches. It turned out that the presence of a few inter-micellar connections sensibly decreases the zero-shear viscosity measured in steady state flow curves. Comparison with oscillatory rheology experiments indicates that the main effect of branches is to shorten the terminal relaxation time by speeding-up the reptation. (Less)
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author
organization
publishing date
type
Contribution to journal
publication status
published
subject
in
Soft Matter
volume
8
issue
42
pages
10941 - 10949
publisher
Royal Society of Chemistry
external identifiers
  • wos:000310829400018
  • scopus:84867385346
ISSN
1744-6848
DOI
10.1039/c2sm26528a
language
English
LU publication?
yes
id
f003d5ea-1b64-4f1e-b951-67be9a93a5b4 (old id 3283281)
date added to LUP
2012-12-20 12:45:01
date last changed
2017-10-01 04:25:22
@article{f003d5ea-1b64-4f1e-b951-67be9a93a5b4,
  abstract     = {We present an investigation on the effect of inter-micellar connections (branches) on the rheology of wormlike micelles. The system chosen is made of lecithin, minute amounts of water and organic solvents. Lecithin and water self-assemble into wormlike reverse micelles that can be branched or unbranched depending on the oil composition (and on the water content). In this respect, cyclohexane favours disconnected reverse micelles while isooctane promotes the formation of branches. By using mixtures of cyclohexane and isooctane as the oil phase and different water/lecithin ratios, the branch density of the system can be finely tuned. PGSE-NMR experiments allowed us to distinguish between branch-free (unbranched) and branched systems and the response of the very same samples to mechanical stress was measured by rheology. This allows, for the first time, an experimental correlation between rheological properties and the presence of branches. It turned out that the presence of a few inter-micellar connections sensibly decreases the zero-shear viscosity measured in steady state flow curves. Comparison with oscillatory rheology experiments indicates that the main effect of branches is to shorten the terminal relaxation time by speeding-up the reptation.},
  author       = {Angelico, Ruggero and Amin, Samiul and Monduzzi, Maura and Murgia, Sergio and Olsson, Ulf and Palazzo, Gerardo},
  issn         = {1744-6848},
  language     = {eng},
  number       = {42},
  pages        = {10941--10949},
  publisher    = {Royal Society of Chemistry},
  series       = {Soft Matter},
  title        = {Impact of branching on the viscoelasticity of wormlike reverse micelles},
  url          = {http://dx.doi.org/10.1039/c2sm26528a},
  volume       = {8},
  year         = {2012},
}