Tailoring of ionic supramolecular assemblies based on ammonium carboxylates toward liquid-crystalline micellar cubic mesophases

Ionic liquid crystals based on ionic complexation of tris(2-aminoethyl)amine (1) with 3,4,5-tris(7,7,8,8,9,9,10,10,11,11,12,12,12-tridecafluorododecyloxy)benzoic acid (2) and with 3,4,5-tris(2-octyldodecyloxy)benzoic acid (3) were investigated. The ionic complex with the partially fluorinated alkyl chains (12) exhibited a morphological transition from a hexagonal columnar mesophase to a Pm3n micellar cubic phase upon increasing the molar ratio of 2 to 1. For the complex with the branched alkyl chains (13) a micellar cubic mesophase was exclusively generated at appropriate composite ratios. The generation of the micellar cubic mesophases is attributed to the introduction of the laterally expanded volume of the alkyl chains compared with the corresponding normal dodecyl chains. Their thermal stabilities were most enhanced at a specific molar ratio of 1:5 for 12 and 1:4 for 13. This result corresponds to the most suitable chain volume for the stable micellar cubic mesophase.