p-Alkoxybiphenyls with guanidinium head groups displaying smectic mesophases

Abstract

Novel calamitic guanidinium salts with p-alkoxybiphenyl or p-alkoxyphenyl core unit (7, 11, 12) have been synthesised, utilising the corresponding nitro compounds as synthetic intermediates. Differential scanning calorimetry (DSC), polarising optical microscopy (POM) and temperature-dependent X-ray diffraction studies reveal smectic A (SmA) mesophases for all series. Whereas the p-alkoxybiphenyl guanidinum chlorides 7 display SmA phases with a minimum chain lengths of C8 and broad mesophase width from 80°C (for C8 derivative 7b) up to 180°C (for C16 derivative 7g), the corresponding p-alkoxyphenyl guanidinium chlorides 11 display much smaller mesophase width from 4°C (for C10 derivative 11c) up to 72°C (for C16 derivative 11e). For the series 12 a large influence of the anion on the clearing point is observed, with clearing points ranging from 209°C for the guanidinium chloride 7f down to 127°C for guanidinium hexafluorophosphate 12d.

Keywords:

• ionic liquid crystal
• guanidinium salts
• smectic
• X-Ray experiments
• calamitic

Acknowledgements

Generous financial support from the Bundesministerium für Bildung und Forschung (grant number 01 RI 05177), the Ministerium für Wissenschaft, Forschung und Kunst des Landes Baden-Württemberg, the European Community (ERASMUS fellowship for S. Saliba) and the Fonds der Chemischen Industrie is gratefully acknowledged.