Synthesis and properties of allyloxy-based tolane liquid crystals with high negative dielectric anisotropy

ABSTRACT

A series of tolane liquid crystals (LCs) containing 2,3-difluorophenyl and allyloxy terminal groups have been synthesised via multi-step reactions. Their thermotropic mesophases, birefringences and dielectric anisotropy properties are discussed by comparison with the non-fluorinated analog. The results show that the allyloxy-based tolane LC 3TOV reveals a high value of the birefringence (0.29), negative dielectric anisotropy (−4.44) and a broad nematic mesophase with a low melting point and high clearing point. The effects of the terminal alkyl chains, the lateral fluoro substituents, the allyloxy terminal group and alkyne bridge on the mesomorphic and physical properties were also discussed. Meanwhile, Density Functional Theory (DFT) calculations of molecular conformation and polarisability were used to correlate the experimental findings.

GRAPHICAL ABSTRACT

KEYWORDS:

• Tolane liquid crystals
• 2
• 3-ortho-difluorophenyl
• allyloxy group
• DFT calculations

Acknowledgement

We are grateful to Professor Wenliang Wang at Shaanxi Normal University for theoretical calculations.

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

The authors would like to thank the Defense Industrial Technology Development Program of China [B0520132007, B1120132028], Joint Fund of Ministry of Education [6141A02022219], National Science Foundation Committee of China [21673134, 21543012] and the Fundamental Research Funds for the Central Universities [GK201704008] for financial support of this work.