Dielectric spectroscopy of liquid crystalline unsymmetrical azomethines with one imine bond: influence of rod length and type of terminal chains

Abstract

In this work we have studied the dielectric properties of five unsymmetrical azomethine (A1−A5) liquid crystals prepared from different aldehydes or obtained from various amines. The effects of rod length and type of terminal chains on the thermal and mesomorphic behaviours were investigated by dielectric spectroscopy. The wide frequency range dielectric spectroscopy confirmed the phase transition detected in an earlier study. Moreover, a relaxation behaviour was detected in three compounds in various phases, which was connected to a particular dipolar group present in these materials, in contrast to two other compounds having a similar molecular structure but lacking strong dipolar groups. The relaxation processes changed their character or disappeared during the phase transition.

Keywords:

• Liquid crystals
• dielectric properties
• azomethines
• Schiff bases