The effect of phenyl ring on the physical properties of liquid crystals containing 4-pyridyl terminal group

ABSTRACT

Liquid crystals with 4-pyridyl end group containing one triple bond and phenylenes have been synthesised. Their structures were confirmed by traditional spectroscopic methods. The properties were measured by differential scanning calorimetry (DSC), polarising optical microscopy (POM), Abbe refractometer and an electrical constants instrument. The results show that all of the compounds exhibit nematic phase. The addition of a phenylene to the molecular skeleton brings about an obvious increase of the mesophase intervals (from 8.8 to 95.5) and birefringence (up to 0.33), as well as minus or plus effect of dielectric anisotropies depending on the position of the phenylene. Density Functional Theory (DFT) calculations of molecular conformation, polarisability and dipole moment were used to further study the molecular structure–property relationship.

Graphical Abstract

KEYWORDS:

• Nematic liquid crystals
• high birefringence
• large dielectric anisotropy
• 4-pyridyl
• DFT calculations

Acknowledgments

We are grateful to Professor Wenliang Wang at Shaanxi Normal University for theoretical calculations. Research was supported by Joint Fund of Ministry of Education (6141A02022219), the Natural Science Foundation of China (21543012, 21673134), the State Education Ministry and the Fundamental Research Funds for the Central Universities (GK201704008).

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

This work was supported by the Natural Science Foundation of China [21543012, 21673134];the State Education Ministry and the Fundamental Research Funds for the Central Universities [GK201704008];Joint Fund of Ministry of Education [6141A02022219];