Synthesis and characterization of hexamethylenetetramine-based ionic liquid crystals

A series of hexamethylenetetramine-based ionic liquid crystals (ILCs) containing cholesterol derivatives and different anions including Br-1, BF4-1, PF6-1, H2PO4-, CF3COO-, TsO-, and CSA-SO3- were synthesized, and the characterization, possible applications and self-assembly behavior were discussed. The ILCs were synthesized from bromine-containing precursor liquid crystal, which was made of cholesterol and 4-bromobutyryl chloride. The ILCs showed smectic A (SmA) mesophase. For these hexamethylenetetramine-containing ILCs, T-g, T-i and liquid-crystalline temperature range reduced slightly in sequence of Br-1, BF4-1, PF6-1, H2PO4-, CF3COO-, TsO-, and CSA-SO3- anions. But the d-spacing of the lamellar structure in SmA phase increased in this sequence of these anions. Because of microphase separation and ionic electrostatic attraction, the SmA layers and self-assembly were formed in these ILCs. The ionic conductivities of the ILCs significantly increased in SmA phase due to unique facilitated ion transport pathways of lamellar ionic channels. (C) 2018 Elsevier B.V. All rights reserved.