期刊
LIQUID CRYSTALS
卷 43, 期 8, 页码 1135-1147出版社
TAYLOR & FRANCIS LTD
DOI: 10.1080/02678292.2016.1161093
关键词
Ionic liquid crystal; ILC; smectic C; mesophase; biphenyl; guanidinium
资金
- Deutsche Forschungsgemeinschaft [LA907/17-1]
- Ministerium fur Wissenschaft, Forschung und Kunst des Landes Baden-Wurttemberg
- Bundesministerium fur Bildung und Forschung [01 RI 05177]
- European Commission (ERASMUS fellowship for Nina Trbojevic)
A series of ionic liquid crystals with an alkoxy biphenyl unit tethered via an alkyl spacer to a guanidinium head group were synthesised and the mesomorphic properties were studied by differential scanning calorimetry, polarising optical microscopy and X-ray diffraction (XRD; WAXS and SAXS). Whereas all symmetrical guanidinium chlorides with the same chain lengths in alkyl tail and spacer displayed enantiotropic SmA(2) phases, monotropic SmC2 phases with 1-2 K temperature range were only formed for chain lengths >= C-10. Shifting the calamitic core more closely to the ionic head group by decreasing the tether length and simultaneously increasing the terminal alkyl chain improved the stability of both SmA and SmC phases considerably and led to enantiotropic SmC phases for the guanidinium chloride with C-14 alkyl tail and C-6 spacer. An even more pronounced effect was detected during anion exchange. Bromide, iodide, hexafluorophosphate, thiocyanate and triflate suppressed any SmC phase, whereas tetrafluoroborate behaved similar to chloride maintaining the SmC phase. However, acetate stabilised the SmC phase at the expense of the SmA phase. Based on temperature-dependant XRD measurements, a bilayer structure was proposed. [GRAPHICS] .
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