Organic nanotubes created from mesogenic derivatives.

A facile route to prepare nanotubes from rod-like mesogens dissolved in typical organic solvents is reported. For selected types of chiral rod-like molecules, nanotubes were formed from both enantiomers and racemic mixtures by slow evaporation from solution, regardless of the solvent, concentration or deposition type. The obtained supramolecular assemblies were studied using AFM, TEM and SEM techniques, and other experimental techniques (IR, UV-Vis spectroscopy and X-ray diffraction) were also applied.

Filaments in the twist-grain-boundary smectic-A phase.

A model of filaments of the twist-grain-boundary smectic-A phase (TGBA) arising from the homeotropic smectic-A phase and nucleating on the sample surface is proposed. The model is based on the concept of finite blocks of parallel smectic layers forming a helical structure. The blocks are surrounded by dislocation loops.

Unique effect of an electric field on a new liquid crystalline lactic acid derivative.

A new chiral lactic acid derivative is presented, exhibiting a frustrated liquid crystalline phase, namely the orthogonal twist grain boundary TGBA phase in a broad temperature interval. A unique effect is observed that the applied electric field reversibly transforms the planar TGBA texture to the homeotropic one, homogeneously dark in crossed polarizers. The transformation is analogous to the Frederiks transition known in nematics, in which switching under electric field is driven by the positive dielectric anisotropy.

Model of dark conglomerate structure in the B2 phase of bent-shape molecules.

Texture observations in B2 phase of bent-shape molecules showed a coexistence of so-called dark conglomerate (DC) structure with fan-shaped texture composed of focal conic domains (FCDs). A model of DC structure based on grains of dimensions lower than visible wavelengths is proposed and used to compare the energies of DC and FCD structures. The comparison of energies of both structures enables the estimation of approximate model parameters.

Binary mixtures of liquid crystalline compounds with a reentrant smectic-A* phase.

Binary mixtures of chiral liquid crystalline homologs have been studied. One compound designated 9ZBL exhibited reentrancy of a paraelectric smectic-A* phase, SmA*(RE), below the ferroelectric SmC* phase in the SmA*-SmC*-SmA*RE phase sequence. Stabilization of the SmA(RE) phase is established from studying binary mixtures of 9ZBL with its neighboring homologs 8ZBL and 10ZBL.

Stripe and line textures in the B2 phase of bent-shape molecules in samples with polar surface anchoring.

In the B2 phase formed by bent-shaped molecules a dense line texture is frequently observed. For the texture description a model is proposed consisting of a periodic system of anticlinic antiferroelectric bulk domains with opposite chiralities separated by π walls in which polarization rotates. The bulk domains are situated between layers of synclinic ferroelectric phase near the upper and lower surfaces.

Reentrant orthogonal smectic-A phase below a tilted smectic-C phase in a chiral compound.

A reentrant orthogonal smectic-A (SmA) phase below the tilted smectic-C phase is established in a chiral liquid crystalline compound. The temperature evolution of the layer spacing confirms monolayer structure in both SmA phases, the upper SmA as well as the reentrant SmA phase. The reentrancy of the SmA phase is explained on the basis of the mean field free energy taking into account nonmonotoneous temperature dependence of the lowest term coefficient.

Communication: Experimental proof of symmetry breaking in tilted smectics composed of molecules with axial chirality.

For the first time, domains with twisted structures have been established in planar samples of achiral compounds in tilted smectic C phase. This evidences separation of molecular conformers differing in the sense of axial chirality and confirms polar C(2) symmetry of these domains. A simple model considering polar surface anchoring energy and bulk energy of the twist can account for this finding.

Orientational and structural properties of ferroelectric liquid crystal with a broad temperature range in the SmC(*) phase by (13)C NMR, x-ray scattering and dielectric spectroscopy.

Thermotropic liquid crystalline materials laterally substituted by a methyl group on the aromatic ring of the alkoxybenzoate unit far from the chiral centre exhibit a very broad temperature range in the ferroelectric smectic C* (SmC(*)) phase on cooling (including supercooling) with a very high spontaneous polarization (∼210 nC cm(-2)) and tilt angle (∼43°) at saturation. We are presenting a detailed study of the physical properties of a ferroelectric compound, representative of this category of liquid crystals, by means of solid state (13)C-NMR, small angle x-ray scattering, dielectric spectroscopy and optical methods of the tilted SmC(*). Values of the spontaneous tilt angle measured optically are compared to those determined from the x-ray data and discussed.

Nature of smectic A*-C* phase transitions in a series of ferroelectric liquid crystals with little smectic layer shrinkage.

The smectic layer spacing of two homologous series of ferroelectric liquid crystal compounds was characterized by small-angle x-ray diffraction and different degrees of smectic layer shrinkage on cooling from the SmA* into the SmC* phase were observed. The smectic A*-smectic C* phase transition was further studied by measuring the thermal and electric field effects on the optical tilt angle and the electric polarization. With decreasing length of the alkyl terminal chain the phase transition changes from tricritical exhibiting high layer shrinkage to a pure second-order transition with almost no layer shrinkage.

Structural and orientational properties of the ferro, antiferroelectric, and re-entrant smectic C phases of ZLL7/ by deuterium NMR and other experimental techniques.

In this work, two selectively deuterium-labeled isotopomers of the (S)-2-methylbutyl- [4'-(4' '-heptyloxyphenyl)-benzoyl-4-oxy-(S)-2-((S)-2')-benzoyl)-propionyl)]-propionate (ZLL 7/), one labeled on the phenyl ring (ZLL 7/-phe-D2) and the other one on the biphenyl fragment (ZLL 7/-biphe-D2), have been investigated by deuterium NMR (DNMR) spectroscopy and other experimental techniques. These compounds possess the paraelectric SmA, the ferroelectric SmC, the antiferroelectric SmC(A), the re-entrant ferroelectric SmC(re), and the ferroelectric hexatic phases down to room temperature. The orientational ordering properties of the two labeled fragments have been determined by means of DNMR, and the mesophase behavior at two magnetic fields is discussed.