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Aqueous phase behavior of salt-free catanionic surfactants: the influence of solubility mismatch on spontaneous curvature and balance of forces

Silva, Bruno F. B.; Marques, Eduardo F. and Olsson, Ulf LU (2011) In Soft Matter 7(1). p.225-236
Abstract
In this paper, we investigate the phase behavior and microstructure for a series of salt-free catanionic surfactants of the type Cm+Cn- with varied chain length mismatch (m not equal n), using light microscopy, DSC, turbidity, surface tension, SAXS and SANS. The compounds consist of alkyltrimethylammonium alkylsulfonates, denoted by TA(m)So(n). Depending on the asymmetry between both ions, three regimes can be identified: (i) weakly asymmetric; (ii) approximately symmetric; and (iii) highly asymmetric. For the TA(16)So(n) compounds, with n = 8 and 9 (weakly asymmetric), the surfactant forms a lamellar phase in water, however, with a striking miscibility gap. This miscibility gap is a consequence of the concentration dependent bilayer... (More)
In this paper, we investigate the phase behavior and microstructure for a series of salt-free catanionic surfactants of the type Cm+Cn- with varied chain length mismatch (m not equal n), using light microscopy, DSC, turbidity, surface tension, SAXS and SANS. The compounds consist of alkyltrimethylammonium alkylsulfonates, denoted by TA(m)So(n). Depending on the asymmetry between both ions, three regimes can be identified: (i) weakly asymmetric; (ii) approximately symmetric; and (iii) highly asymmetric. For the TA(16)So(n) compounds, with n = 8 and 9 (weakly asymmetric), the surfactant forms a lamellar phase in water, however, with a striking miscibility gap. This miscibility gap is a consequence of the concentration dependent bilayer charge density. For n = 8, also a temperature-dependent vesicle-to-micelle transition at low surfactant concentration is observed. When the mismatch is low (n = 10) only a non-swelling lamellar phase is formed (approximately symmetric regime). For high mismatch, (n = 6 and 7) an extensive micellar phase is obtained - highly asymmetric regime. Conversely, for the TA(m)So(8) compounds, where m = 12 and 14, the unconventional lamellar miscibility gap and vesicle-micelle transition are again present. These findings are rationalized by considering the effect of film charge density-arising from the chain solubility difference-on the spontaneous curvature and balance of colloidal forces. The type of phase behavior reported here should be extensive to other families of salt-free catanionic amphiphiles, where an appropriate tuning of the solubility mismatch can allow the control of self-assembly. (Less)
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author
organization
publishing date
type
Contribution to journal
publication status
published
subject
in
Soft Matter
volume
7
issue
1
pages
225 - 236
publisher
Royal Society of Chemistry
external identifiers
  • wos:000285360200030
  • scopus:78650338137
ISSN
1744-6848
DOI
10.1039/c0sm00477d
language
English
LU publication?
yes
id
015734db-de28-4b93-9e6e-87b3ac3242e8 (old id 1773926)
date added to LUP
2011-02-01 10:26:10
date last changed
2017-10-22 04:04:49
@article{015734db-de28-4b93-9e6e-87b3ac3242e8,
  abstract     = {In this paper, we investigate the phase behavior and microstructure for a series of salt-free catanionic surfactants of the type Cm+Cn- with varied chain length mismatch (m not equal n), using light microscopy, DSC, turbidity, surface tension, SAXS and SANS. The compounds consist of alkyltrimethylammonium alkylsulfonates, denoted by TA(m)So(n). Depending on the asymmetry between both ions, three regimes can be identified: (i) weakly asymmetric; (ii) approximately symmetric; and (iii) highly asymmetric. For the TA(16)So(n) compounds, with n = 8 and 9 (weakly asymmetric), the surfactant forms a lamellar phase in water, however, with a striking miscibility gap. This miscibility gap is a consequence of the concentration dependent bilayer charge density. For n = 8, also a temperature-dependent vesicle-to-micelle transition at low surfactant concentration is observed. When the mismatch is low (n = 10) only a non-swelling lamellar phase is formed (approximately symmetric regime). For high mismatch, (n = 6 and 7) an extensive micellar phase is obtained - highly asymmetric regime. Conversely, for the TA(m)So(8) compounds, where m = 12 and 14, the unconventional lamellar miscibility gap and vesicle-micelle transition are again present. These findings are rationalized by considering the effect of film charge density-arising from the chain solubility difference-on the spontaneous curvature and balance of colloidal forces. The type of phase behavior reported here should be extensive to other families of salt-free catanionic amphiphiles, where an appropriate tuning of the solubility mismatch can allow the control of self-assembly.},
  author       = {Silva, Bruno F. B. and Marques, Eduardo F. and Olsson, Ulf},
  issn         = {1744-6848},
  language     = {eng},
  number       = {1},
  pages        = {225--236},
  publisher    = {Royal Society of Chemistry},
  series       = {Soft Matter},
  title        = {Aqueous phase behavior of salt-free catanionic surfactants: the influence of solubility mismatch on spontaneous curvature and balance of forces},
  url          = {http://dx.doi.org/10.1039/c0sm00477d},
  volume       = {7},
  year         = {2011},
}