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ABSTRACT
In this work, 14 pyridinium and imidazolium-based ionic liquid crystal (ILC) with azo (N=N) and acetylene (C≡C) as linking group were synthesised in high yields and completely characterised. The structure of the molecules were planned in order to allow a complete investigation on how modifications such as presence and position of charges, linking group, number of alkoxy chains and their length affect the thermal stability and liquid crystalline behaviour. All compounds were thoroughly investigated using polarised optical microscopy (POM), differential scanning calorimetry (DSC), X-ray diffraction (XRD) measurements and thermogravimetric analysis (TGA). While the presence of charges favoured a liquid crystalline behaviour, especially SmA (and SmA2) phase, a decrease of thermal stability was noticed. A strong dependence of the charge position and a preference for monolayer or bilayer molecular organisation was observed. On the other hand, it was demonstrated that the addition of a second alkoxy chain promoted layer distortions in some molecules, resulting in the formation of Smà and Cub phases. Also a direct comparison between the N=N and C≡C linking groups was realised, along with further comparison with literature data. The structure–properties are investigated in detail.
Graphical Abstract
Acknowledgements
The authors are grateful to CAPES and CNPq for financial support, LDRX-CFM/UFSC for the free access to the XRD equipment and CEBIME for the HRMS analysis. We also thank Prof. Adailon J. Bortoluzzi for the single crystal XRD measurements, and Prof. Hugo Gallardo and Prof. Carsten Tschierske for fruitful discussions.
Disclosure statement
No potential conflict of interest was reported by the authors.
Supplemental material
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