Hockey Stick Liquid Crystals Based on a 2,5-Asymmetric Disubstituted [1,3,4]Oxadiazole Core

Abstract

The article describes the liquid-crystalline properties of some 2,5-asymmetric disubstituted [1,3,4]oxadiazole derivatives containing an azo and an ester linkage obtained through esterification of 2-(4-methoxyphenyl)-5-(4-hydroxyphenyl)-[1,3,4]oxadiazole with a series of 4-(4-alkoxyphenyl)-benzoic acids containing 6–10 and 18 aliphatic carbon atoms. All reported compounds present liquid-crystalline properties, evidenced by differential scanning calorimetry (DSC) and polarizing optical microscopy (POM), with nematic and smectic C type structures, with very large range of stability of mesophases (between 130°C and 198°C on heating and 134°C and 214°C on cooling).

Keywords:

• asymmetric [1,3,4]oxadiazole
• bent-core
• hockey stick liquid crystals

Acknowledgment

This work was supported by CNCSIS-UEFISCSU (Romania), project number PNII-IDEI 356/2008.

Notes

Abbreviations: K, crystal; LC, liquid crystal; I - isotropic.

*Data obtained from POM investigations.

** T_onse, temperature at which thermal degradation begins.