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Mix-and-match diols: adjusting self-assembly of micellar phases in choline chloride eutectics
Authors:
Oliver
Hammond
(University of Bath)
,
Adrian
Sanchez-Fernandez
(University of Bath)
,
Rachel
Tyte
(University of Bath)
,
Robert
Dalgliesh
(ISIS Neutron and Muon Source)
,
Andrew J.
Smith
(Diamond Light Source)
,
Karen
Edler
(University of Bath)
Co-authored by industrial partner:
No
Type:
Journal Paper
Journal:
Crystals
, VOL 12
State:
Published (Approved)
Published:
November 2022
Diamond Proposal Number(s):
15194

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, 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.
Diamond Keywords: deep eutectic solvents; surfactants; self-assembly; liquid crystals; small-angle scattering
Subject Areas:
Chemistry
Instruments:
I22-Small angle scattering & Diffraction
Other Facilities: Larmor at ISIS
Added On:
17/11/2022 10:20
Documents:
crystals-12-01621.pdf
Discipline Tags:
Chemistry
Technical Tags:
Scattering
Small Angle X-ray Scattering (SAXS)