Anticlinic smectic phase formed by calamitic hydrazide derivatives with terminal hydroxyl group

Abstract

A new series of liquid crystalline hydrazide derivatives N-4-(alkoxyphenyl)-N'-4-[(4-hydroxyphenyl)azophenyl] benzohydrazide (BNB-n, n = 8, 12, 14) was designed and synthesised. Based on the results of variable temperature ¹H NMR and FT-IR spectroscopy, a supramolecular assembly motif of BNB-n through both axial intermolecular hydrogen bonds between hydroxyl groups and lateral hydrogen bonds between hydrazide groups was proposed. Interestingly, BNB-n (n = 12, 14) with longer terminal chains displayed anticlinic bilayer smectic C mesophase (SmC_2a). In order to reveal the effect of axial hydrogen bonding between hydroxyl groups on the formation of this unique mesophase, the hydroxyl group was replaced by a methoxy group to form N-4-(alkoxyphenyl)-N'-4-[(4-methoxyphenyl)azophenyl] benzohydrazide (BNBC-n, n = 12, 14). However, BNBC-n showed synclinic monolayer smectic C (SmC_s) features, suggesting that the hydroxyl groups in BNB-n have an important role in the formation of anticlinic molecular packing in the smectic layers.

Keywords:

• hydrazide
• intermolecular hydrogen bonds
• SmC_2a mesophase
• SmC_s mesophase

Acknowledgements

The authors are grateful to the National Science Foundation Committee of China for their financial support of this work (Project No. 50873044, 51073071, 21072076), and Project 985-Automotive Engineering of Jilin University for their financial support of this work.