Phase diagram, dielectric and electro optic properties of binary liquid crystals mixtures

ABSTRACT

Nematic phase at room temperature with wide stability and high birefringence is particularly desirable for functional devices. Two thermotropic liquid crystals (tolane and the 4-pentyl-4-biphenylcarbonitrile nematic also known as 5CB) are mixed by varying the weight fraction (wt%) in order to investigate the phase sequences and their physical properties using differential scanning calorimetry (DSC), polarised optical microscopy (POM) and dielectric spectroscopy techniques. Phase coexistence was observed for a concentrations 20 ≤ C ≤ 60 wt% of tolane in 5CB and the phase diagram was established. In addition, the nematic-isotropic temperature T_NI increases with increasing the concentration of tolane LCs. A eutectic mixture at room temperature with large nematic range and high birefringence is obtained for C = 10 wt%. The increase in the nematic range is due to an enhancement of the nematic order induced by the LCs. It is found that the electro optical parameters like the threshold voltage, the response time were relatively increased. This increment can be attributed to an increase in the viscoelastic properties of the mixture.

Graphical abstract

KEYWORDS:

• Nematic
• phase diagram
• coexistence phases
• eutectic mixtures

Acknowledgments

The authors extend their appreciation to the Deanship of Scientific Research at Imam Mohammad Ibn Saud Islamic University for funding this work through Research Group no. RG-21-09-67.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Additional information

Funding

The work was supported by the The authors extend their appreciation to the Deanship of Scientific Research at Imam Mohammad Ibn Saud Islamic University for funding this work through Research Group no. RG-21-09-67 [RG-21-09-67].