Changes of thermo-morphologic and thermotropic properties of liquid crystals at direct and reverse nematic mesophase ↔ isotropic liquid phase transitions: surface-induced effect

Abstract

In this work, the effect of thin films on the thermo-morphologic and thermotropic properties of the phase transitions between the nematic mesophase and isotropic liquid has been investigated. Investigations have been carried out for both the heating and cooling processes. The temperature and linear widths of the biphasic regions of the direct and reverse phase transitions in nematic liquid crystals versus thickness of the thin films have been calculated with a high accuracy. The shift of the nematic mesophase–isotropic liquid and the isotropic liquid–nematic mesophase phase transition temperatures to higher temperatures and the enlargement of the temperature and linear widths of the biphasic regions as the effect of surfaces have been found.

Keywords:

• liquid crystals
• phase transitions
• thermotropic properties
• surface effect
• biphasic region
• thin films

Acknowledgement

The author is grateful to Dr M. Tepe (Department of Physics, Ege University) for technical assistance.