Mesomorphic Hydrogen‐Bonded Complexes of Complementary Semiperfluorinated Components

Abstract

2,4-Diamino-6-phenyl-1,3,5-triazines carrying one or two semiperfluorinated chains at the phenyl substituent have been investigated in binary mixtures with partially fluorinated benzoic acids by polarizing microscopy, differential scanning calorimetry, and X-ray diffraction. The number and positions of the fluorinated tails of the acid component were systematically modified. Equimolar mixtures of the triazines with the aromatic acids form discrete hydrogen-bonded heterodimers with an elongated central core. Mesomorphic properties are observed only if at least three terminal fluoroalkyl chains are grafted to the hydrogen-bonded rigid core. The dimeric supermolecules exhibit columnar mesophases with rectangular or oblique two-dimensional lattice symmetry or bicontinuous cubic phases. The mesophases of the dimers are ribbon phases resulting from the collapse of smectic layers. Thereby, the phase type is defined by the number and positions of the fluorinated tails of the two components. Docking of two or three equivalents of two-chain benzoic acids to the diaminotriazine core leads to the formation of cylindrical aggregates, which organize into hexagonal columnar phases, whereas 1:2 and 1:3 mixtures of the two-chain triazine with a three-chain fluorinated aromatic acid display micellar cubic phases.

Ionic Liquid Crystals: Versatile Materials

“…Mixtures of 167- n with 1,3,5-triazine or with 2,4,6-triamino-1,3,5-triazine show macroscopic segregation and no LC properties. LC hydrogen-bonded complexes of substituted 2,6-diamino-1,3,5-triazines, 2,6-diamino-4-arylamino-1,3,5-triazines, and 2,4,6-triarylamino-1,3,5-triazines with semifluorinated benzoic acid derivatives have also been reported, but FT-IR measurements did not point to genuine ionic interactions in those compounds. − …”

Discotic Liquid Crystals

“…Upon addition of protic solvents such as formamide, the Cub I2 phase was replaced by a lyotropic columnar mesophase. Mixtures with semiperfluorinated benzoic acids provided phase sequences of Col r and Col ob geometries. , Furthermore, H-bonded complexes of biphenyl-substituted triazines with semiperfluorinated benzoic acids formed Col h phases when two side chains are present. − Mixtures displayed broader and more stable mesophases than the pure compounds. The results were rationalized by a “first-order” effect arising from the molar content of the acid component which defines the molecular geometry of the H-bonded polar central core.…”

“…Mixtures with semiperfluorinated benzoic acids provided phase sequences of Col r and Col ob geometries. 332,333 Furthermore, H-bonded complexes of biphenyl-substituted triazines with semiperfluorinated benzoic acids formed Col h phases when two side chains are present. 334−336 Mixtures displayed broader and more stable mesophases than the pure compounds.…”

Helical self-assembly and co-assembly of fluorinated, preorganized discotics

“…38 Mesophase behaviour of hydrogen-bonded, alkylated triazines and benzoic acids has been tuned by variation of the ratio between fluorinated and hydrogenated tails. 39, 40 An advantage of these intermolecularly hydrogen bonded systems is that with a limited number of precursors a wide variety of liquid crystalline materials are accessible. In solution, fluorinated porphyrin 41 and phthalocyanine 42 derivatives have been reported that possess potential gas or drug carrier applications.…”