Bent‐core mesogens based on semi‐flexible dicyclohexylmethane spacers

New, bent‐core mesogens are described in which the core of the molecule is a semiflexible, di(4‐aminocyclohexyl)methane spacer. The compounds show nematic, columnar nematic and columnar phases as shown by a combination of X‐ray diffraction and optical microscopy. The potential of these new mesogens as biaxial nematic candidates is considered.     

Comparing investigation of the smectic C and A phases of the di-n-alkyl 4,4′-azoxycinnamates (II) X-ray studies

The paper continues the investigation of the smectic C and A phases of the title compounds which has been done in Part I by DSC calorimetry. Here the layer spacings in the S_C and S_A phases are presented which exhibit a remarkable different temperature dependence in the S_C phases within the homologous series. A tendency of a change from a second order S_C/S_A transition to a first order transition has been found. The layer spacings of the S_A phase show a chain length dependent difference to the lengths of the molecules which may be explained by an increasing amount of gauche conformations in the higher homologues.     

Molecular Design of Liquid-Crystalline Block Molecules: Semifluorinated Pentaerythritol Tetrabenzoates Exhibiting Lamellar, Columnar, and Cubic Mesophases

Fluid assemblies of star-shaped molecules like 1 form a range of thermotropic liquid crystalline phases, and represent a borderline case between anisometric mesogens, surfactants, and block copolymers. The low molecular mass molecules (<5.5 kDa) consist of a semipolar central core and a shell of semifluorinated chains.     

Re-entrant isotropic behaviour of a pure double-swallow-tailed compound

Two new six-ring double-swallow-tailed mesogens were prepared. The phase behaviours of these compounds were studied by optical methods and by calorimetry. One of them shows the very unusual phase sequence crystalline-smectic C-cubic-isotropic-nematic-isotropic.     

Band-structure modulation in carbon nanotube T junctions

We show that the band structure of metallic carbon nanotubes can be dramatically altered by the local electrostatic field. This is realized by coupling chemically functionalized nanotubes to form T junctions. The bar of the T is the conducting channel and the leg of the T is used for local gating. Transport measurements reveal that an energy gap develops upon application of a local electric field in both devices with or without linker molecules at the junction. We propose that the mechanism of the band gap modulation in the T junctions without linker molecules is the field effect, with the linker molecules introducing additional electromechanical and chemical effects.