CHARGE-TRANSFER INDUCED NEMATIC COLUMNAR PHASE IN LOW-MOLECULAR-WEIGHT DISK-LIKE SYSTEMS

Two large pentakis(phenylethynyl)phenyl alkyl ethers, without side chains as is usual for discotic systems, were synthesized in palladium catalysed one pot coupling reactions. These low molecular weight and non-liquid-crystalline electron donor compounds were doped with 2,4,7-trinitrofluorenone under the formation of charge transfer complexes. The induction of two types of enantiotropic mesophases (i.e. nematic and hexagonal columnar phases (N(c) and D(ho)) was observed. These charge transfer-induced mesophases were characterized by polarization microscopy, differential scanning calorimetry, and X-ray analysis; phase diagrams of the binary systems were also recorded as well as the hexagonal columnar to nematic columnar transition as a function of the length of the disturbing alkoxy group. It is considered possible now to study low molecular mass N(c) phases by tailor-made two component mixtures on the basis of our easily accessible disc-shaped multiynes.