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 (1)H 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 (SmC2a). 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 (SmCs) features, suggesting that the hydroxyl groups in BNB-n have an important role in the formation of anticlinic molecular packing in the smectic layers