Pushing steric bias in the Scholl reaction to access liquid crystalline crown ethers.

Sterically congested o-terphenyl crown ethers with alkoxy substituents at the 2,3,4-position or 3,4,5-position were synthesized from the corresponding tetrabromodibenzo[15]crown-5 and the corresponding boronic acids or borolanes via Suzuki cross-coupling and subsequently cyclized to the corresponding triphenylenes utilizing the Scholl reaction. Both series of compounds were investigated by differential scanning calorimetry, polarizing optical microscopy, and X-ray diffraction (SAXS, WAXS) regarding their mesomorphic properties. While all but one of the 3,4,5-substituted derivatives displayed liquid crystalline behavior (Col(h) and Col(r)), only the 2,3,4-substituted triphenylene with the shortest alkoxy chains was liquid crystalline (Col(r)).

Ionic liquid crystals derived from amino acids.

Novel chiral amino acid derived ionic liquid crystals with amine and amide moieties as spacers between the imidazolium head group and the alkyl chain were synthesised. The key step in the synthesis utilised the relatively uncommon SO3 leaving group in a microwave-assisted reaction. The mesomorphic properties of the mesogens were determined by differential scanning calorimetry (DSC), polarising optical microscopy (POM) and X-ray diffraction.

Synthesis of guanidinium-sulfonimide ion pairs: towards novel ionic liquid crystals.

The recently introduced concept of ionic liquid crystals (ILCs) with complementary ion pairs, consisting of both, mesogenic cation and anion, was extended from guanidinium sulfonates to guanidinium sulfonimides. In this preliminary study, the synthesis and mesomorphic properties of selected derivatives were described, which provide the first example of an ILC with the sulfonimide anion directly attached to the mesogenic unit.

Triphenylene silanes for direct surface anchoring in binary mixed self-assembled monolayers.

New triphenylene-based silanes 2-(ω-(chlorodimethylsilyl)-n-alkyl)-3,6,7,10,11-penta-m-alkoxytriphenylene 4 (Tm-Cn) with n = 8 or 9 and m = 7, 8, 9, 10, or 11 were synthesized, and their self-assembly behavior in the liquid state and at glass and silicon oxide surfaces was investigated. The mesomorphic properties of triphenylene silanes 4 (Tm-Cn) and their precursors 3 (Tm-Cn) were determined by differential scanning calorimetry (DSC), polarizing optical microscopy (POM), and X-ray diffraction. From the small-angle X-ray scattering (SAXS) regime, a preferential discotic lamellar mesophase can be deduced, and wide-angle X-ray scattering (WAXS) highlights the liquid-like characteristics of the alkyl side chains.