Mesophase Morphologies of Hydrogen-Bonded Complexes of Biphenyl-Substituted Diamino-1,3,5-triazines with Semiperfluorinated Benzoic Acids

Two 2,4-diamino-6-biphenyl-4-yl-1,3,5-triazines carrying either one semiperfluorinated or two lipophilic alkoxy chains at the terminal position of the biphenyl moiety have been investigated in binary mixtures with two-chain and three-chain partially fluorinated benzoic acids by means of polarizing microscopy, differential scanning calorimetry, and X-ray diffraction. Equimolar compositions of the triazines with the complementary two-chain benzoic acid form descrete hydrogen-bonded heterodimers. The dimeric supermolecules organize to rectangular columnar phases in the c 2 mm plane group. The Col r phases are composed of infinite ribbons of parallel aligned H-bonded rigid polar cores which are separated by aliphatic/fluorinated regions. H-bonded associates of the fluorinated triazine with three equivalents of the two-chain acid form a rectangular columnar phase ( p 2 m symmetry). Replacing the one fluorinated chain of the triazine by two alkoxy groups leads to a columnar phase on a two-dimensional square lattice ( p 4 mm ) in a 1:3 mixture with the two-chain benzoic acid. The 1:3 mixed systems of the triazines with the three-chain aromatic acid display micellar cubic phases.