Columnar liquid crystalline benzenetrisamides with pendant 1,3,4-oxadiazole groups

Abstract

Novel liquid crystal materials based on 1,3,5-benzenetrisamide derivatives with three pendant 2-phenyl-5-(mono-, di-, and/or tri-n-alkoxyphenyl)-1,3,4-oxadiazole arms (Ia–c, IIa–c) were prepared. The mesomorphic properties of these compounds were characterised and studied by differential scanning calorimetry, polarising optical microscopy and X-ray diffraction. The formation of a columnar mesophase was found to be dependent on the number of alkoxy side chains. The compounds Ib and IIb, with a total of six alkoxy chains, and compounds Ic and IIc, with nine alkoxy chains, exhibited an enantiotropic hexagonal columnar (Col_h ) phase with high isotropisation temperatures; however, compounds Ia and IIa with a total of three alkoxy chains formed a crystalline phase. Compounds IIb and c were room temperature liquid crystals.

Keywords:

• liquid crystals
• 1,3,4-oxadiazoles
• benzenetrisamides
• mesophases
• hexagonal columnar phase

Acknowledgements

This work was supported by FONDECYT (grant 1070535), “Dirección de Investigación, Universidad de Concepción” and the MICINN-FEDER Spanish Project CTQ 2009–09030.