Unexpected observation of an intermediate hexagonal phase upon fluid-to-gel transition: SDS self-assembly in glycerol

Lauren Matthews, Michael C Stevens, Ralf Schweins, Paul Bartlett, Andrew. J Johnson, Robert Sochon, Wuge H Briscoe*

*Corresponding author for this work

Research output: Contribution to journalLetter (Academic Journal)peer-review

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Abstract

Understanding morphological transformations upon temperature-induced mesophase transitions offers mecha-nistic insights into the self-assembly process. We have recently reported the unexpected formation of a micro-fibrillar lamellar gel in SDS-glycerol mixtures above a critical gelation concentration (CGC) as low as ~2 wt%. The gel phase comprised a fibrillar structure on the microscale and a lamellar structure on the nanoscale. Here, the nanoscopic structure of the gel as a function of temperature was probed with small-angle neutron scattering (SANS). The gel underwent a gel-to-fluid transition at a critical gelation temperature, TGC =45 ◦C, forming cylindrical micelles at elevated temperatures. Upon cooling, a hexagonal phase formed at ~TGC, evident from the SANS Bragg peaks. This hexagonal phase upon the fluid-to-gel transition sheds light on the gelation mechanism, in which self-assembled SDS micelles undergo a cylindrical-to-lamellar morphological transition via a hexagonal phase. This unprecedented observation also highlights the complexity of self-assembly in nonaqueous hydrogen- bonding rich media.
Original languageEnglish
Article number100342
Number of pages5
JournalColloid and Interface Science Communications
Volume40
Early online date13 Dec 2020
DOIs
Publication statusPublished - 1 Jan 2021

Keywords

  • Glycerol
  • SDS
  • Surfactant mesophases
  • Nonaqueous H-bonding solvents
  • Small-angle neutron scattering
  • Self-assembly
  • Gelation
  • Low molecular-weight gels
  • Lamellar phase
  • Hexagonal phase

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