Thermal and mesomorphic properties of ternary mixtures of some hydrogen-bonded liquid crystals

Abstract

The thermal and mesophase behaviour of ternary mixtures formed from hydrogen-bonded nematic liquid crystals 4-hexylbenzoic acid, 4-(octyloxy)benzoic acid and 4-(decyloxy)benzoic acid were investigated by differential scanning calorimetry (DSC) and phases identified by polarised optic microscopy (POM). The DSC and POM results clearly indicate that the produced mixtures display liquid crystalline properties. The phase transition temperature values obtained in the DSC experiments are in line with the POM observations. Investigation of the thermal properties of ternary mixtures reveals that the nematic range of the produced mixtures is affected in a way that is dependent on both the mixture ratio and the difference in the alkyloxy chain lengths. Furthermore, the phase transition temperature values of ternary mixture increase with increasing heating rate, and the calculated activation energy values show that the reaction arising during the phase transitions of the mixture is regular.

Keywords:

• liquid crystals
• phase transitions
• thermal properties
• microstructure

Funding

We would like to thank the Kahramanmaras Sutcu Imam University Scientific Research Projects Coordination for its financial support, Project No. 2011/3-43 D, and Prof. Dr Süleyman Yılmaz for his technical assistance with POM measurements.