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Effect of Oligomerization of Counterions on Water Activity in Aqueous Cationic Surfactant Systems

Kocherbitov, Vitaly LU and Söderman, Olle LU (2016) In Journal of Physical Chemistry B 120(28). p.6961-6968
Abstract

A sorption calorimetry study of cationic cetyltrimethyl ammonium surfactants with four different counterions was performed. The counterions were acetate, succinate, citrate, and butyl tetracarboxylate with formal charges ranging from 1 to 4, respectively. The counterions with 2-4 charges can be considered as oligomers. In all the cases, hydration experiments started with dry solid phases that upon water uptake went through solid-state phase transitions and hexagonal to micellar cubic phase transitions. It was found that in liquid-crystalline phases the activity of water increased with the degree of oligomerization or, equivalently, the formal charge of the counterions. The results are discussed in terms of the forces acting between the... (More)

A sorption calorimetry study of cationic cetyltrimethyl ammonium surfactants with four different counterions was performed. The counterions were acetate, succinate, citrate, and butyl tetracarboxylate with formal charges ranging from 1 to 4, respectively. The counterions with 2-4 charges can be considered as oligomers. In all the cases, hydration experiments started with dry solid phases that upon water uptake went through solid-state phase transitions and hexagonal to micellar cubic phase transitions. It was found that in liquid-crystalline phases the activity of water increased with the degree of oligomerization or, equivalently, the formal charge of the counterions. The results are discussed in terms of the forces acting between the colloidal aggregates. It is argued that under the conditions investigated, the so-called strong-coupling theory can be used to describe the electrostatic forces between the charged colloidal objects. Therefore, we suggest that the observed dependence of water activity on the degree of polymerization is due to the entropy of mixing of the counterions in the water volume, which we describe using Flory-Huggins theory.

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author
organization
publishing date
type
Contribution to journal
publication status
published
subject
in
Journal of Physical Chemistry B
volume
120
issue
28
pages
8 pages
publisher
The American Chemical Society
external identifiers
  • scopus:84978629996
  • wos:000380590900006
ISSN
1520-6106
DOI
10.1021/acs.jpcb.6b03104
language
English
LU publication?
yes
id
25ef9fe3-5f3b-4c76-b448-516a0a3e9d61
date added to LUP
2017-01-09 09:27:56
date last changed
2017-10-22 05:24:41
@article{25ef9fe3-5f3b-4c76-b448-516a0a3e9d61,
  abstract     = {<p>A sorption calorimetry study of cationic cetyltrimethyl ammonium surfactants with four different counterions was performed. The counterions were acetate, succinate, citrate, and butyl tetracarboxylate with formal charges ranging from 1 to 4, respectively. The counterions with 2-4 charges can be considered as oligomers. In all the cases, hydration experiments started with dry solid phases that upon water uptake went through solid-state phase transitions and hexagonal to micellar cubic phase transitions. It was found that in liquid-crystalline phases the activity of water increased with the degree of oligomerization or, equivalently, the formal charge of the counterions. The results are discussed in terms of the forces acting between the colloidal aggregates. It is argued that under the conditions investigated, the so-called strong-coupling theory can be used to describe the electrostatic forces between the charged colloidal objects. Therefore, we suggest that the observed dependence of water activity on the degree of polymerization is due to the entropy of mixing of the counterions in the water volume, which we describe using Flory-Huggins theory.</p>},
  author       = {Kocherbitov, Vitaly and Söderman, Olle},
  issn         = {1520-6106},
  language     = {eng},
  month        = {07},
  number       = {28},
  pages        = {6961--6968},
  publisher    = {The American Chemical Society},
  series       = {Journal of Physical Chemistry B},
  title        = {Effect of Oligomerization of Counterions on Water Activity in Aqueous Cationic Surfactant Systems},
  url          = {http://dx.doi.org/10.1021/acs.jpcb.6b03104},
  volume       = {120},
  year         = {2016},
}