Effect of bent-shape and calamitic-shape of hydrogen-bonded mesogens on the liquid crystalline properties

Abstract

Six series of hydrogen-bonded (H-bonded) liquid crystals (LCs) were synthesised to study the effect of H-bonded mesogens with calamitic-shape or bent-shape structure on mesogenic behaviours by using isonicotinate and nicotinate derivatives as proton acceptors. The lateral fluoro-substituent and the length of the terminal chains were also studied in detail. When the structure of H-bonded LCs changed from calamitic-shape to bent-shape, the length to breadth ratio reduced greatly, which led to the temperature range of mesophases narrowed and a decrease in melting point and clear point. Although the introduction of fluorine substituent could reduce the length to breadth ratio and lead to the mesophase range narrowed, even disappeared, it could effectively inhibit the emergence of the smectic A phase and obviously enhance the strength of H-bond self-assembly. Additionally, it could help reduce the phase transition points to increase the length of terminal chains.

Keywords:

• calametic-shape
• liquid crystal
• hydrogen-bond
• bent-shape
• self-assembly

Additional information

Funding

This work was supported by the National Natural Science Foundation of China [grant numbers 61370048, 51333001, 51173017, 51203011, 51103010]; the Fundamental Research Funds for the Central Universities [grant number FRF-TP-14-013A2]; the Major Project of International Cooperation of the Ministry of Science and Technology [grant number 2013DFB50340]; the Beijing Higher Education Young Elite Teacher Project [grant number YETP0356].