Mesomorphic block molecules: Semiperfluorinated 1,3,5-triazine derivatives exhibiting lamellar, columnar, and cubic mesophases

New 2,4-diamino-6-phenyt-1,3,5-triazines carrying one or two semiperfluorinated chains at the phenyl substituent have been synthesized. The thermotropic liquid crystalline properties of the compounds were investigated by polarizing microscopy, differential scanning calorimetry, and X-ray diffraction. The single-chain compounds exhibit a lamellar (SmA) mesophase with intercalation of the polar rodlike aromatic subunits. The two-chain partially fluorinated triazine forms a reverse discontinuous (micellar) cubic phase (Cub(12)). Additionally, binary mixtures of a single-chain triazine with the two-chain semi perfluorinated triazine were investigated. Inverted bicontinuous Cubic (Cub(V2)) and hexagonal columnar (Col(h2)) phases are induced as intermediate between the lamellar and the micellar cubic mesophases of the pure compounds. On addition of protic solvents such as formamide, the Cub(12) phase of the two-chain triazine is replaced by a lyotropic columnar mesophase.