Thermal and current–voltage behaviour of liquid crystal compounds with rod and bent shapes comprising alkoxysemifluorinated and imine segments

Abstract

The synthesis and mesomorphic properties of a series of thermotropic liquid crystalline symmetrical rod and bent-shaped imines containing two long alkoxysemifluorinated chains were reported. Three different diamines varying in the number of phenylene rings from 1 to 3 were used to understand structure–mesomorphic property correlation. Differential scanning calorimetry, X-ray diffraction and polarised optical microscopy were used to determine their phase transition behaviour. An enantiotropic smectic phase was observed for all the systems studied. The thermal properties of the azomethines were discussed in relation to the core shape and length of the core. Current–voltage measurements were performed on ITO/compound/Alq₃/Al and ITO/TiO₂/compound/Alq₃/Al devices before and after irradiation with light (about 1000 W m⁻²). To prepare the TiO₂ layer, the sol-gel technique was applied.

Keywords:

• imines
• azomethines
• Schiff bases
• mesomorphic behaviour
• fluorine compounds
• bent-shaped and rodlike compounds

Acknowledgement

The authors thank Dr. Patrice Rannou for the POM experiments.