The influences of lateral groups on 4-cyanobiphenyl-benzonitrile- based dimers

ABSTRACT

Cyanobiphenyl-based compounds are known to display RT or low melting liquid crystals in a single-component system or composites. Herein, we discuss the influence of laterally substituted groups (-CN, -F, -H) on 4-[ω-(4-cyanobiphenyl-4’-yloxy)alk-1-yloxy]benzonitrile. Three series of new dimers were synthesised by using 4-cyano-4’-hydroxybiphenyl connected via flexible spacers with different number of carbon atoms to 4-hydroxyphthalonitrile/ 2-fluoro-4-hydroxy benzonitrile/ 4-hydroxy benzonitrile. Their self-assembly in LC phases assessed by polarising optical microscopy (POM), differential scanning calorimetry (DSC) and X-ray diffraction studies, and their behaviours are compared with related non-substituted (-H) model compound. UV-Visible and fluorescent experiments confirm the strong aggregation, the intensities of emission decrease as we move from CN→F→H substitutions. A representative dimer from each series covering the aspect of polarity and flexibility have been simulated using 1000 minimisation steepest descent and CHARMM force filed to examine their self-assembly. This work helps to understand the influence of lateral groups, connecting spacers on the LC behaviour of dimers.

Graphical abstract

KEYWORDS:

• Liquid crystals
• dimers
• cyanobiphenyl
• nematic phase
• fluorescence
• aggregation
• molecular dynamic simulation

Acknowledgements

G Shanker thanks Science and Engineering Research Board (SERB), Government of India, for the financial support through ECR project No. ECR/2016/001224. Also acknowledged BANGALORE UNIVERSITY, Jnana Bharathi Campus, Bengaluru-560056 with UNI.ORDER.No.Dev:D2a:BU-RP:2021 for their support. Thanks to the Faculty Recharge Programme, University Grants Commission (UGC-FRP), New Delhi, INDIA.

Disclosure statement

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

Supplementary material

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Additional information

Funding

This work was supported by the Science and Engineering Research Board [ECR/2016/001224].