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.
This research is in part supported by the NSF EPSCoR RING-TRUE III grant no. 0447416, NSF-SBIR grant no. OII-0610753, NSF-STTR grant no. IIP-0740289 and NASA GRC contract no. NNX10CD25P (PKB). We thank Ronald C. G. Principe for making the Figures and Tables for this article. Acknowledgment is made to the donors of the American Chemical Society Petroleum Research Fund grant no. 59345-ND7 for partial support of this research by CMR and MRF. AMF would like to thank the Carnegie Trust for the Universities of Scotland, for the Research Incentive Grant RIG008586, the Royal Society and Specac Ltd., for the Research Grant RGS\R1\201397, and the Royal Society of Chemistry for the award of a mobility grant (M19-0000).
- Ionic liquid crystals
- Differential scanning calorimetry
- Polarizing optical microscopy
- Variable temperature X-ray diffraction
- Smectic T phase
- Ionic conductivity