Mesomorphism of novel stilbene-based bent-core liquid crystals

ABSTRACT

A series of asymmetric bent-core liquid crystals, bearing the stilbene moiety in the side wing, was synthesised and characterised. Structural modifications of the non-stilbene wing resulted in formation of various mesophases. Compounds 1 and 3 with an ester linking group between the phenyl rings in this wing have an enantiotropic non-polar smectic-type mesophase, while compound 2, incorporating the biphenyl moiety, has a ferroelectric SmC_aP_F phase. The molecules of 2 undergo photoisomerisation in solution under UV irradiation, while the mesophases are unstable and UV irradiation leads to irreversible changes. The mesophases of 1 and 3 do not show any electro-optical switching and polarisation current. Applying low frequency AC voltage on a planarly aligned film of compound 2, smectic domains grow, while the birefringence and an image flickering increase. The observed features of these compounds identify stilbene as an attractive moiety in the design of advanced materials based on bent-core molecules.

Graphical abstract

KEYWORDS:

• Bent-core liquid crystals
• stilbene
• photoresponsive materials
• structure–property relationship

Acknowledgments

This work was supported by the US. National Science Foundation (NSF) DMR-1904167. The beamline 6.3.3 at the Advanced Light Source at the Lawrence Berkeley National Laboratory is supported by the Director of the Office of Science, Office of Basic Energy Sciences, of the US. Department of Energy under Contract No. DE-AC02- 05CH11231. N.T. and L.M. are grateful to the Ministry of Education, Science and Technological Development of the Republic of Serbia for financial support (Contract No. 451-03-68/2020-14/200135; 451-03-68/2020-14/200287). T.T.-K. acknowledges the financial support from the National Research, Development and Innovation Office (NKFIH) grant no. FK 125134. R.S. and A.J. acknowledge useful discussions and technical help by Dr Chenhui Zhu, Professor Sam Sprunt and Mr Prabesh Gyawali.

Disclosure statement

No potential conflict of interest was reported by the authors.

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Additional information

Funding

This work was supported by the US. National Science Foundation (DMR-1904167), the Ministry of Education, Science and Technological Development of the Republic of Serbia (Contract No. 451-03-68/2020-14/200135; 451-03-68/2020-14/200287) and the National Research, Development and Innovation Office of Hungary (NKFIH; grant no. FK 125134).