Four ring achiral ferroelectric liquid crystals of 1,2,4-oxadiazoles: synthesis and characterisation

ABSTRACT

A novel series of four-ring achiral ferroelectric liquid crystals containing 1,2,4-oxadiazole cores with unsymmetrical substitutions at C-3 and C-5 positions are synthesised and characterised. A fluoro substituted biphenyl moiety is prepared by Suzuki coupling reaction and is directly attached to the oxadiazole core at the C-5 position for the first time in the literature. An octyl benzoate is attached to the oxadiazole core at the C-3 position of it. All the compounds exhibit polar smectic (B₂) mesophases with ferroelectric switching along with the orthogonal smectic-A mesophases. These compounds possess high mesomorphic thermal ranges of polar smectic phases and are towards the ambient temperatures. The influence of a more electronegative fluorine substituent on the electron rich biphenyl moiety (at the C-5 position) of the oxadiazole core is analysed for the prevalence and abundance of polar smectic (ferroelectric) mesophases.

GRAPHICAL ABSTRACT

KEYWORDS:

• Achiral liquid crystals
• Suzuki coupling
• smectic-A phase
• B₂ phase
• ferroelectric nature
• spontaneous polarisation
• mesomorphic thermal ranges

Acknowledgements

We are grateful to Management of Syngene international Ltd., Bangalore; Manipal University, Manipal, and JNTUK, Kakinada, for infrastructural facilities. Also, the Doctoral Advisory Committee (DAC) members of Mahabaleshwara for their valuable suggestions is acknowledged.

Disclosure statement

No potential conflict of interest was reported by the authors.

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Additional information

Funding

Our gratitude to DST [DST/SR/S2/CMP-0063/2008], Govt. of India for financial support.