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Mix-and-Match Diols: Adjusting Self-Assembly of Micellar Phases in Choline Chloride Eutectics

Hammond, Oliver S. ; Sanchez-Fernandez, Adrian LU orcid ; Tyte, Rachel ; Dalgliesh, Robert ; Smith, Andrew J. and Edler, Karen J. LU orcid (2022) In Crystals 12(11).
Abstract

The common Deep Eutectic Solvent (DES) ‘ethaline’ (1:2 choline chloride:ethylene glycol) was examined here as a basis for the self-assembly of the surfactant dodecyltrimethylammonium bromide (C12TAB). A phase diagram was constructed, showing evidence for a L1 (micellar) phase, confirmed by tensiometry to have a room temperature critical micelle concentration (CMC) of 1.2 wt.%. Small angle neutron scattering (SANS) measurements indicate formation of interacting globular micelles with slightly smaller apparent radii than in water. The apparent mesophase/multiphase region was studied using SWAXS, demonstrating rich mesoscopic lyotropic liquid crystalline phase behaviour, with evidence for lamellar Lα peaks,... (More)

The common Deep Eutectic Solvent (DES) ‘ethaline’ (1:2 choline chloride:ethylene glycol) was examined here as a basis for the self-assembly of the surfactant dodecyltrimethylammonium bromide (C12TAB). A phase diagram was constructed, showing evidence for a L1 (micellar) phase, confirmed by tensiometry to have a room temperature critical micelle concentration (CMC) of 1.2 wt.%. Small angle neutron scattering (SANS) measurements indicate formation of interacting globular micelles with slightly smaller apparent radii than in water. The apparent mesophase/multiphase region was studied using SWAXS, demonstrating rich mesoscopic lyotropic liquid crystalline phase behaviour, with evidence for lamellar Lα peaks, alongside potential co-crystalline phases. We attempted to tailor the self-assembly by studying binary DES containing longer diols including 1,2-propanediol, 1,3-propanediol, 1,4-butanediol, and 1,5-pentanediol, and ternary DES where the HBD component was a 1:1 ethylene glycol:diol mixture. However, synchrotron SAXS showed that only ternary ‘propethaline’ mixtures displayed signs of self-assembly and micellization, perhaps due to the reduction in calculated Gordon parameter, which decreases linearly with increasing alkyl chain length. Systematic differences were thus observed in the ability of the solvents to modulate assembly, from globular micelles in ChCl:EG, to weaker assembly in long-tail DES, and complete solubilisation in butaline and pentaline.

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author
; ; ; ; and
publishing date
type
Contribution to journal
publication status
published
keywords
deep eutectic solvents, liquid crystals, self-assembly, small-angle scattering, surfactants
in
Crystals
volume
12
issue
11
article number
1621
publisher
MDPI AG
external identifiers
  • scopus:85149480031
ISSN
2073-4352
DOI
10.3390/cryst12111621
language
English
LU publication?
no
additional info
Publisher Copyright: © 2022 by the authors.
id
76ec99c2-7c87-48bb-b854-ccab1d71537f
date added to LUP
2023-03-29 11:21:11
date last changed
2023-03-30 15:11:06
@article{76ec99c2-7c87-48bb-b854-ccab1d71537f,
  abstract     = {{<p>The common Deep Eutectic Solvent (DES) ‘ethaline’ (1:2 choline chloride:ethylene glycol) was examined here as a basis for the self-assembly of the surfactant dodecyltrimethylammonium bromide (C<sub>12</sub>TAB). A phase diagram was constructed, showing evidence for a L<sub>1</sub> (micellar) phase, confirmed by tensiometry to have a room temperature critical micelle concentration (CMC) of 1.2 wt.%. Small angle neutron scattering (SANS) measurements indicate formation of interacting globular micelles with slightly smaller apparent radii than in water. The apparent mesophase/multiphase region was studied using SWAXS, demonstrating rich mesoscopic lyotropic liquid crystalline phase behaviour, with evidence for lamellar L<sub>α</sub> peaks, alongside potential co-crystalline phases. We attempted to tailor the self-assembly by studying binary DES containing longer diols including 1,2-propanediol, 1,3-propanediol, 1,4-butanediol, and 1,5-pentanediol, and ternary DES where the HBD component was a 1:1 ethylene glycol:diol mixture. However, synchrotron SAXS showed that only ternary ‘propethaline’ mixtures displayed signs of self-assembly and micellization, perhaps due to the reduction in calculated Gordon parameter, which decreases linearly with increasing alkyl chain length. Systematic differences were thus observed in the ability of the solvents to modulate assembly, from globular micelles in ChCl:EG, to weaker assembly in long-tail DES, and complete solubilisation in butaline and pentaline.</p>}},
  author       = {{Hammond, Oliver S. and Sanchez-Fernandez, Adrian and Tyte, Rachel and Dalgliesh, Robert and Smith, Andrew J. and Edler, Karen J.}},
  issn         = {{2073-4352}},
  keywords     = {{deep eutectic solvents; liquid crystals; self-assembly; small-angle scattering; surfactants}},
  language     = {{eng}},
  number       = {{11}},
  publisher    = {{MDPI AG}},
  series       = {{Crystals}},
  title        = {{Mix-and-Match Diols: Adjusting Self-Assembly of Micellar Phases in Choline Chloride Eutectics}},
  url          = {{http://dx.doi.org/10.3390/cryst12111621}},
  doi          = {{10.3390/cryst12111621}},
  volume       = {{12}},
  year         = {{2022}},
}