Ordering properties of oligomeric columnar discotic liquid crystals

The synthesis and liquid crystalline ordering properties of oligomeric discotic liquid crystals were investigated. The phase behaviour and surface ordering properties are dependent on among others core type, spacer length and fluorination. </p

Ordering properties of columnar discotic triazines containing three pendant triphenylenes with four or five fluorinated trials

Two series of discotic columnar liquid crystals were prepared and investigated, consisting of a triazine core to which three triphenylenes (HATs) are attached, connected via a flexible variable spacer containing a triazole group. The triphenylenes have five pentafluoropentyloxy tails or four pentafluoropentyloxy tails and one methoxy group. The compounds with four fluorinated tails on the HAT groups show a lamellar-columnar phase (Collam), whereas a compound with five fluorinated tails on the HAT groups shows a hexagonal-columnar (Colh) phase. Small differences in the steric properties and fluorophobic effects can therefore have a strong influence on the ordering of the molecules in the liquid crystalline phase

Fluorine-containing triphenylenes. Liquid crystalline properties and surface ordering

The synthesis and liquid crystalline properties of two novel series of triphenylenes with 4 or 5 pentafuoropentyloxy tails and 1 or 2 alkoxy tails of varying length are reported. All compounds form wide-range hexagonal columnar phases. The isotropisation temperatures and the corresponding enthalpy changes for the compounds with 4 or 5 fluorinated tails are higher than for the compounds with 6 alkoxy tails, and also higher than for compounds with 6 fluorinated tails. These results indicate that the best ordering is obtained for compounds with a mix of fluorinated and non-fluorinated tails. With increasing length of the alkyl tails in HAT compounds with 4 or 5 fluoroalkoxy tails, the isotropisation temperatures decrease and the d-spacings as observed by XRD increase. All fluorocontaining compounds have a strong tendency for spontaneous homeotropic alignment on surfaces, both hydrophilic and hydrophobic

Discotic liquid crystalline tris(hexahexyloxytriphenylene)triazines with separate columns of triphenylene and triazine cores

A series of novel discotic liquid crystal compounds containing three pendent triphenylenes connected to a triazine core via spacers of different length that were linked via a triazole group as obtained from an azide–alkyne click reaction was investigated. All compounds of the series exhibit wide-range columnar phases from room temperature to more than 100°C. X-ray reflection measurements indicate an ordering with separate columns of the triazine and triphenylene cores. Quantum chemical calculations confirmed the significant contributions of the triazine and triazole groups to the p–p stacking in the columns. This type of organisation reveals an additional feature of triazole-forming click chemistry and indicates interesting properties for optoelectronic applications