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A binary mixture of two disc-like liquid crystals 2, 3, 7, 8, 12, 13-hexa-n-tetradecanoyloxy and 2, 3, 7, 8, 12, 13-hexa (4-n-dodecyloxybenzoyloxy) truxenes exhibits an isotropic phase above and below the temperature existence range of a columnar mesophase.

We present the first example of disc-like mesogens which present at high temperature a highly fluid mesophase with a nematic optical texture. These nematic disc-like compounds are pure simple component models to study the carbonaceous mesophase.

The phase behaviour under pressure of two disc-like mesogens are studied with a metabolemeter. The investigated compounds are (-)-2,3,6,7,10,11-hexa-[S-(3-methyl)-n-nonanoyloxy] triphenylene and 2,3,6,7,10,11-hexa-(n- dodecanoyloxy) triphenylene. The weakly first order or practically second order mesomorphic transitions are detected. The pressure-temperature phase diagrams are established. The volume changes for the first order phase transitions are determined.

Several chiral disc-like compounds are described. They exhibit nonchiral D columnar phases. But it is shown that, for example, chiral triphenylenes are able to twist the ND nematic phase of a hexabenzoate of triphenylene. That is, probably, the first evidence of a “cholesteric” phase in disc-like mesogens.

New disc-like mesogens are presented which are three hexa-n-alkanoates of truxene. A fluid phase is observed below a columnar viscous phase with respect to temperature. Perhaps the first example of a reentrant nematic phase in disc-like compounds?