Ionic liquid crystals: synthesis and characterization via NMR, DSC, POM, X-ray diffraction and ionic conductivity of asymmetric viologen bistriflimide salts

Pradip K. Bhowmik* (Corresponding Author), Omar Noori, Si L. Chen, Haesook Han, Michael R. Fisch, Christina M. Robb, Alfonso Martinez-Felipe

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

Abstract

A series of asymmetric viologen bistriflimide salts of both short and long alkyl chains were synthesized by the metathesis reaction of lithium triflimide salt with the respective asymmetric viologen dibromide salts in methanol. Their thermotropic liquid crystalline were determined by differential scanning calorimetry, polarizing optical microscopy and variable temperature X-ray diffraction techniques. These salts melt into highly-ordered smectic T phases that is, crystal-to SmT transitions (Tms) at relatively low temperatures (lowest Tm at −12 °C) and maintain liquid crystallinity in a wide range of temperatures (8–132 °C), with excellent thermal stabilities up to 320 °C as determined by thermogravimetric analysis. These results differ with respect to the symmetric viologen bistriflimide salts. Ionic conductivity of these salts was also measured by dielectric impedance spectroscopy and found to be in the 10–2.43 S cm−1 range, highlighting their potential as electrolytes at room temperature.
Original languageEnglish
Article number115370
Number of pages10
JournalJournal of molecular liquids
Volume328
Early online date12 Jan 2021
DOIs
Publication statusPublished - 15 Apr 2021

Keywords

  • Ionic liquid crystals
  • Differential scanning calorimetry
  • Polarizing optical microscopy
  • Variable temperature X-ray diffraction
  • Smectic T phase
  • Ionic conductivity

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