Synthesis and characterization of hexamethylenetetramine-based ionic liquid crystals

Abstract A series of hexamethylenetetramine-based ionic liquid crystals (ILCs) containing cholesterol derivatives and different anions including Br −1 , BF 4 −1 , PF 6 −1 , H 2 PO 4 − , CF 3 COO − , TsO − , and CSA-SO 3 - 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 , BF 4 −1 , PF 6 −1 , H 2 PO 4 − , CF 3 COO − , TsO − , and CSA-SO 3 - 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.