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The influence of n-hexanol on the morphology and composition of CTAB micelles

Schmutzler, Tilo; Schindler, Torben; Schmiele, Martin; Appavou, Marie Sousai; Lages, Sebastian LU ; Kriele, Armin; Gilles, Ralph and Unruh, Tobias (2018) In Colloids and Surfaces A: Physicochemical and Engineering Aspects 543. p.56-63
Abstract

The effect of the addition of n-hexanol as co-surfactant on the structure of cetyltrimethylammonium bromide (CTAB) micelles has been studied using small-angle X-ray and neutron scattering (SAXS, SANS). Contrast variation neutron scattering experiments were performed to determine the structure of both pure CTAB and n-hexanol modified CTAB micelles. The incorporation of n-hexanol leads to an elongation of the ellipsoidal CTAB micelles. The scattering length density of the micellar shell linearly depends on the degree of deuteration of the dispersion medium water and revealed the existence of substantial amounts of water in the micellar shell. The water content in the shell increased from 20 vol-% observed for pure CTAB micelles to 44... (More)

The effect of the addition of n-hexanol as co-surfactant on the structure of cetyltrimethylammonium bromide (CTAB) micelles has been studied using small-angle X-ray and neutron scattering (SAXS, SANS). Contrast variation neutron scattering experiments were performed to determine the structure of both pure CTAB and n-hexanol modified CTAB micelles. The incorporation of n-hexanol leads to an elongation of the ellipsoidal CTAB micelles. The scattering length density of the micellar shell linearly depends on the degree of deuteration of the dispersion medium water and revealed the existence of substantial amounts of water in the micellar shell. The water content in the shell increased from 20 vol-% observed for pure CTAB micelles to 44 vol-% found for n-hexanol modified CTAB micelles. The amount of n-hexanol in the micellar shell was determined by varying the amount of fully deuterated and protonated n-hexanol. These experiments revealed a volume fraction of 26 vol-% of n-hexanol molecules in the micellar core which equals a molar fraction of 50 % n-hexanol within the CTAB micelles. The total composition of micellar core and shell was estimated. The packing density of headgroups, water molecules and bromide ions turned out to drastically increase in n-hexanol modified CTAB micelles. These findings contribute to a fundamental understanding of the stabilization mechanism of micelles by alcoholic co-surfactants and the resulting alteration of the morphology and interface composition. These results will facilitate the optimization of processes where CTAB and other comparable surfactants are used as phase transfer catalysts, structure directing agents or stabilizers in colloidal dispersions or emulsions.

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author
organization
publishing date
type
Contribution to journal
publication status
published
subject
keywords
Co-surfactants, CTAB micelles, SANS, SAXS, Surfactants
in
Colloids and Surfaces A: Physicochemical and Engineering Aspects
volume
543
pages
8 pages
publisher
Elsevier
external identifiers
  • scopus:85041439191
ISSN
0927-7757
DOI
10.1016/j.colsurfa.2017.12.039
language
English
LU publication?
yes
id
89f12f0c-6cea-48b0-b3fb-c38350af4942
date added to LUP
2018-02-20 09:52:30
date last changed
2018-05-29 09:25:08
@article{89f12f0c-6cea-48b0-b3fb-c38350af4942,
  abstract     = {<p>The effect of the addition of n-hexanol as co-surfactant on the structure of cetyltrimethylammonium bromide (CTAB) micelles has been studied using small-angle X-ray and neutron scattering (SAXS, SANS). Contrast variation neutron scattering experiments were performed to determine the structure of both pure CTAB and n-hexanol modified CTAB micelles. The incorporation of n-hexanol leads to an elongation of the ellipsoidal CTAB micelles. The scattering length density of the micellar shell linearly depends on the degree of deuteration of the dispersion medium water and revealed the existence of substantial amounts of water in the micellar shell. The water content in the shell increased from 20 vol-% observed for pure CTAB micelles to 44 vol-% found for n-hexanol modified CTAB micelles. The amount of n-hexanol in the micellar shell was determined by varying the amount of fully deuterated and protonated n-hexanol. These experiments revealed a volume fraction of 26 vol-% of n-hexanol molecules in the micellar core which equals a molar fraction of 50 % n-hexanol within the CTAB micelles. The total composition of micellar core and shell was estimated. The packing density of headgroups, water molecules and bromide ions turned out to drastically increase in n-hexanol modified CTAB micelles. These findings contribute to a fundamental understanding of the stabilization mechanism of micelles by alcoholic co-surfactants and the resulting alteration of the morphology and interface composition. These results will facilitate the optimization of processes where CTAB and other comparable surfactants are used as phase transfer catalysts, structure directing agents or stabilizers in colloidal dispersions or emulsions.</p>},
  author       = {Schmutzler, Tilo and Schindler, Torben and Schmiele, Martin and Appavou, Marie Sousai and Lages, Sebastian and Kriele, Armin and Gilles, Ralph and Unruh, Tobias},
  issn         = {0927-7757},
  keyword      = {Co-surfactants,CTAB micelles,SANS,SAXS,Surfactants},
  language     = {eng},
  month        = {04},
  pages        = {56--63},
  publisher    = {Elsevier},
  series       = {Colloids and Surfaces A: Physicochemical and Engineering Aspects},
  title        = {The influence of n-hexanol on the morphology and composition of CTAB micelles},
  url          = {http://dx.doi.org/10.1016/j.colsurfa.2017.12.039},
  volume       = {543},
  year         = {2018},
}