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Liquid crystals (LCs), whose refractive index can be changed by light irradiation, can be used as photoresponsive optical materials. In this study, an LC viologen was proposed as a novel photoresponsive compound that induced a change in the alignment of LC molecules (mesogens). An extended viologen with an asymmetric core, that exhibits a low-order LC phase at room temperature, was mixed with the well-known nematic LC compound (5CB) to prepare homogeneously aligned films. The change in the alignment of the mesogens was successfully induced by triggering a one-electron reduction reaction of the viologen moieties by light irradiation. [ABSTRACT FROM AUTHOR]

Were formed anisotropic thin films of oligo(p-phenylene vinylene) dye on the surface of rubbed nylon during rod-coating from chloroform and chlorobenzene solutions. The order parameter and alignment direction of films depend on the solvent type and the temperature. On coating from chloroform solution molecules in the dye film align perpendicular and parallel to rubbing direction at temperatures below 40 °C and above 60 °C, correspondingly. Homogeneously oriented anisotropic films with a dichroic ratio of more than 25 were obtained. [ABSTRACT FROM AUTHOR]

We prepared blend alignment film based on 4-ethylphenoxymethyl-substituted polystyrene (P4EP) and polystyrene (PS) for liquid crystal (LC) alignment. Stable and uniform LC cells having pretilt angles adjustable from 90° to 0° were obtained from these polystyrene blend films having weight contents of P4EP and PS of 1 and 100 weight %, respectively. The LC alignment behavior was well correlated with the wettability of the polymer films. These polystyrene blends having good solubility in many organic solvents and their films having low process temperature can be candidates for LC alignment layer in the flexible display. This study contributes to the latest efforts to develop new alignment layers for pretilt angle control. [ABSTRACT FROM AUTHOR]

We synthesized a series of 4-ethylphenoxymethyl (P4EP) and 3-ethylphenoxymethyl (P3EP) and 2-ethylphenoxymethyl-substituted polystyrenes (P2EP), using polymer analogous reactions, in order to study the isomeric effect of the ethylphenoxymethyl side groups on the liquid crystal (LC) alignment properties. The LC cells fabricated with the unrubbed P4EP, P3EP, and P2EP films exhibited uniform vertical, partial vertical, and random planar LC alignment. A high pretilt angle of about 90° was observed from the LC cell prepared from the rubbed film of P4EP at number of rubbing of 1. On the contrary, the LC cells prepared from the rubbed films of P3EP and P2EP showed pretilt angles of approximately 30° and 0° at number of rubbing of 1, respectively. Therefore, the position of ethyl group attached to phenyl group in the side chain was found to LC alignment behavior of the polystyrene derivatives. The LC alignment behavior was well correlated with the wettability of the polymer films. These polystyrene derivatives having good solubility in many organic solvents and their films having low process temperature can be candidates for LC alignment layer in the flexible display. This study contributes to the latest efforts to develop new alignment layers for pretilt angle control. [ABSTRACT FROM PUBLISHER]

The rubbing conditions are researched in terms of the rubbing cloth materials for ferroelectric liquid crystal (FLC) display application. Although cotton is generally used as the rubbing cloth, a good FLC molecular alignment can be obtained even in (semi) synthetic fiber clothes such as acetate, cellulose, and polyester. In order to obtain the good alignment without rubbing scratches, it is important to use a soft cloth. On the other hand, for a hard cloth, there is a possibility to obtain the good alignment by increasing the rubbing number and thus, polishing the alignment film surface. [ABSTRACT FROM AUTHOR]

We prepared blend alignment layer based on 4-ethylphenoxymethyl-substituted polystyrene (P4EP) and polystyrene containing 7-hydroxycoumarin (P7COU) for liquid crystal (LC) alignment. Stable and uniform vertical LC cells having pretilt angles adjustable from 90° to 81.2° were obtained from these polystyrene films having molar contents of P4EP and P7COU in the ranges of 100–70 and 0–30 mol%, respectively. The LC alignment behavior was well correlated with the wettability of the polymer films. These polystyrene blends having good solubility in many organic solvents and their films having low process (curing) temperature can be candidates for LC alignment layer in the flexible display. This study contributes to the latest efforts to develop new alignment layers for pretilt angle control. [ABSTRACT FROM AUTHOR]

We synthesized a series of fluorinated polystyrene (PCMSF#, # = 50, 80, and 100), where # is the molar content of 1H,1H,2H,2H-perfluorodecanethiolate moiety, using polymer analogous reactions to investigate their liquid crystal (LC) alignment properties. In general, the LC cell fabricated using the polymer film having a higher molar content of fluorinated side group showed vertical LC alignment behavior with a pretilt angle of about 90°. The vertical alignment behavior was well correlated with the surface energy value and fluorine atomic percent of these polymer films. For example, vertical alignment was observed when the surface energy values of the polymer were smaller than about 8.77 mJ/m2generated by the nonpolar and long fluorocarbon groups. Good electro-optical characteristics, such as voltage holding ratio (VHR) and residual DC voltage (R-DC), and aligning stabilities at 250°C were observed for the LC cells fabricated using PCMSF100 as a LC alignment layer. [ABSTRACT FROM AUTHOR]

The liquid crystal (LC) alignment behaviors of LC cells fabricated with cellulose acetate films were investigated. These polymer films exhibited good optical transparency in the visible light region (400–700 nm). For example, transmittance value (92%) of the cellulose acetate film onto glass substrate at 550 nm is better that (89%) of the polyimide (PI) film, the most commonly used LC alignment layers. These LC cells fabricated with the rubbed cellulose acetate films showed the homogeneous planar LC alignment with parallel direction with respect to the rubbing direction. The electro-optical characteristics of the LC cells made from the cellulose acetate films such as response time were as good as those fabricated from rubbed PI films. [ABSTRACT FROM AUTHOR]

The present article reports on the alignment or orientation of a particular compound N(4-n-heptyloxy benzylidene)4´-n-butylaniline through dielectric study. The effect of using two different alignment layers (for homogenous alignment) and doping silver nanoparticles (0.25% by weight) on the behavior in dielectric property with varying temperature and biasing electric field was studied in terms of liquid crystal alignment or orientation using the mechanism proposed by earlier workers. The study includes the anomalous dielectric behavior in SmG phase by presenting a technique for the analysis of the absorption process, which exists only in SmG phase at fixed frequency while varying temperature, is also presented. [ABSTRACT FROM AUTHOR]

We performed Monte Carlo simulation of the system consisting of hard spheres, hard spherocylinders and a large hard plate. These elements were used to examine how substrates modified by adsorbed particles affect an alignment of liquid crystal molecules. In order to adsorb the hard spheres on the hard plate, dragging potential for spheres were introduced. We prepared a homogeneous and a homeotropic alignment as an initial configuration of the simulations. Numbers and the size of adsorbed spheres were changed. Results showed that molecular alignment after relaxation depended on the initial configuration even for the same system parameters. We expect that the nematic phase of the present systems favor the homogeneous alignment. This is because we observed cases in which the homeotropic alignment was canceled after relaxation and we never observed cases in which the homogeneous alignment was canceled for the nematic phase of the present systems. [ABSTRACT FROM AUTHOR]

The uniform alignment of liquid crystalline cubic blue phase II (BPII) has been achieved using a conventional surface rubbing treatment. Through comparison of thick and thin cells of assembled rubbed glass, which were covered with commercially available polyimide (PI), we confirmed that rubbed surfaces play an important role in the fabrication of monodomain PBII. These well-aligned cubic BPII materials can be promising for photonics devices. [ABSTRACT FROM AUTHOR]

We synthesized a series of polystyrene derivatives containing coumarin side groups, poly(7-(4-vinylbenzyloxy)coumarin) (P7COU#) and poly(7-(4-vinylbenzyloxy)4-phenylcoumarin) (P7COU4P#), where # is the molar content of 7-hydroxycoumarin and 7-hydroxy-4-phenyl coumarin, respectively, using polymer analogous reaction, in order to study the effect of the 7-hydroxycoumarin and 7-hydroxy-4-phenyl coumarin side groups on the liquid crystal (LC) alignment properties. The LC alignment behavior of these two series was investigated by photoalignment or rubbing alignment. The LC cells made from photoirradiated P7COU# and P7COU4P# films showed homogeneous planar LC alignment. We found that LC aligning ability of the LC cells made from rubbed P7COU# and P7COU4P# films were affected by the structure and molar content of coumarin side groups. For example, anchoring energy of the LC cell fabricated with rubbed P7COU82 (7 × 10−5J/m2) and P7COU4P81 (7 × 10−7J/m2) film was increased drastically and slightly compared to polystyrene (10−7−10−8J/m2), respectively. Particularly, anchoring energy of the LC cell made from rubbed P7COU# having more than 51 mol % of the 7-hydroxycoumarin as a side groups is comparable to that of the conventional polyimide in the LCD industry. [ABSTRACT FROM AUTHOR]

One azotolane-containing acrylate monomer with a longer spacer and a non-azotolane crosslinker were synthesized. Crosslinked liquid crystal polymer (CLCP) films were obtained by thermal polymerization of the mixture of the monomer and the crosslinker with a molar ratio of 2:8. Thermodynamic and mesomorphic properties of the monomer, the crosslinker and the CLCP films were characterized by DSC and POM. The CLCP films showed a low glass transition temperature which ensured them to bend at room temperature upon visible light irradiation. Besides, the films have a faster bending speed compared with the previously-reported azotolane-containing CLCP films with a shorter spacer. [ABSTRACT FROM AUTHOR]

We prepared blend alignment layer based on polystyrene containing 7-hydroxycoumarin (P7COU) and polystyrene containing 2-naphthoxy (P2NAP) side groups for liquid crystal (LC) alignment. The LC cells made from the rubbed P7COU/P2NAP blended films exhibited a shift of the LC alignment direction by approximately 20° compared with those made from a polystyrene film. Stable and homogeneous planar LC cells having pretilt angles adjustable from 0° to 5° were obtained from these polymer films having molar contents of P7COU and P2NAP in the ranges of 100–80 and 0–20 mole%, respectively. The LC alignment behavior was well correlated with the wettability of the polymer films. [ABSTRACT FROM PUBLISHER]

We report the scanning tunnelling microscopy (STM) observation of a self-organization of4-cyano-4′-n-decylbiphenyl(10CB) molecules on the reconstructed Au(111) surface. The self-organized monolayers were obtained by the deposition from a liquid. We revealed a row-like dimer structure with regularly arranged kinks within each dimer row. The separation between neighbor kinks is equal to 4 or 5 intermolecular distances. STM-images with intramolecular resolution showed that the association of molecules in dimers is due to the interaction between cyano groups. The obtained results are discussed in terms of the balance between the molecule-molecule and molecule-substrate interactions and are supported by the results of DFT calculations. [ABSTRACT FROM PUBLISHER]

We present our recent effort on chromonic liquid crystal alignment. In particular, we report the alignment behavior of chromonic molecules using different hydrophobic substrates. Different materials have been used to this purpose but in all cases ribbons textures develop, indicating a slow water evaporation and/or a strong aggregation among molecules, that, as reported in a recent paper, give rise to threads connected through salt bridge bonds. Thin films of materials usually employed for thermotropic liquid crystals alignment induce schlieren textures that after 10 days evolve into ribbon textures; thin films of materials with a low surface energy orient molecules in homeotropic configuration, but the alignment is lost after two weeks as in the case of degenerate planar alignment. [ABSTRACT FROM AUTHOR]

In this article, we propose a mechanical rubbing method to eliminate the optical bounce and decrease the response time of homeotropic liquid crystal cells. After gently rubbing the inorganic alignment film (sputtered silicon oxide, SiO2), the decreasing polar anchoring energy results in a smaller pretilt angle giving liquid crystal a toppling direction to shorten the transition time while liquid crystal cell is applied by an external electric field. The results of our work show that this rubbing remedy suppresses the optical bounce. This simple and efficient surface rubbing treatment could be applied to liquid crystal on silicon technique for projectors and portable displays. [ABSTRACT FROM AUTHOR]

The near-edge X-ray absorption fine structure(NEXAFS) and its polarization dependence on Carbon(C) K-edge, is used to obtain information on the molecular orientation at the polyimide(PI) surface. Rubbed PI alignment layer was controlled the pile contact impression and stage speed. We could estimate the alignment angle α of the molecules with the surface normal of the PI molecules through the intensity change of C=C π* in NEXAFS C K-edge spectrum, depending on the photon incident angle θ = 20°, 55° and 90°. As increasing the depth of the pile contact, the angle α was linearly decreased. The stage speed dependency was shown an irregular pattern. [ABSTRACT FROM AUTHOR]

The anisotropy of the substrate is responsible for inducing alignment of liquid crystal. Several techniques such as mechanical contact, light and plasma irradiation, which can create the anisotropy, are being tried to apply in commercial products. In this research, electron beam irradiation was used to induce liquid crystal alignment. A tilted electron irradiation of around 1016/cm2 supposed to induce planar alignment in a lecithin-coated substrate. Polar anchoring was weakened by one order of magnitude, as compared to a rubbed PI layer, and the azimuthal anchoring was significantly weakened. An electron-beam-irradiated PI layer seemed not to induce the alignment. [ABSTRACT FROM AUTHOR]

X-ray Photoelectron Spectroscopy was applied to study the chemical composition of the modified glass surfaces by the flux of accelerated Ar or Ar/H2 plasma in order to clarify mechanisms of liquid crystal (LC) alignment on these surfaces. It was established that the surface of prinstine glass exposed to air contains carbonaceous contamination layer consisting of about 50% of aliphatic/aromatic carbon and about 50% of C-O moieties of various types. Plasma processing results in partial ablation of this layer and modification of its chemical composition. This suggests that LCs are actually being aligned by the plasma modified carbonaceous layer rather than by a pure glass. [ABSTRACT FROM AUTHOR]

Nanoscale grating patterns coated indium-tin-oxide (ITO) layers were fabricated using the ultraviolet (UV) nano-imprinting technique. The nanoscale groove coated ITO that was prepared in this experiment could play a role in alignment layers and conducting electrodes. Performance for LC alignment was characterized by evaluating order parameter. The LC order parameter evaluated on the fabricated layer was comparable to that of the conventional rubbed polyimide layer. We also confirmed that the 90° twisted nematic liquid crystal (TNLC) cell with our nanopattern coated ITO layer exhibited stable electro-optical performance. [ABSTRACT FROM AUTHOR]

The correlation between nanorelief of polyimide films obliquely treated by the beam of accelerated Ar plasma and liquid crystal (LC) alignment on these films is investigated. It is shown that the plasma beam treatment results in the change of films' roughness in a nanometer scale. In this case, the values of roughness in the directions parallel and perpendicular to the plasma beam projection on the films are different and dependent on the exposure dose. Clear correlation between the anisotropy of surface roughness and the direction of LC alignment is observed. This implies that topology is important, possibly decisive, factor of planar LC alignment on the surfaces obliquely treated by plasma beam. [ABSTRACT FROM AUTHOR]

The alignment of liquid crystal by nano-structured surfaces is investigated. Two methods of preparing the nano-structured inhomogeneous surfaces will be examined. It is shown that this type of surface can give excellent alignment properties. Reliable pretilt angles of any value between 0 and 9° can be obtained. Novel multi-domain structures can also be made in conjunction with photoalignment. These nano-structured alignment layers are very useful for a variety of display applications. [ABSTRACT FROM AUTHOR]

Investigation of the properties of the liquid crystalline polymer (LCP) retarder films, formed by photo-polymerization of a reactive LC mixture at various conditions, has shown that the alignment, the birefringence and the thermal stability of the LCP film are governed by the conversion of photo-polymerization (CP) of reactive LCs. The CP of the LCP film photo-polymerized in air has increased with the intensity of irradiation light, which reduces both the degree of in-plane alignment of LCs and the birefringence but gives the better thermal stability of the film. The photo-polymerization in an inert environment has induced the higher CP and the better thermal stability of the LCP film than the in-air polymerization. [ABSTRACT FROM AUTHOR]

The polymer-stabilized ferroelectric liquid crystal (PS-FLC) photocured under the application of an AC electric field shows a monostable V-shaped electrooptical characteristics. However, it is not clear how the V-shaped electrooptical characteristics can be realized in the PS-FLC. In this study, we have investigated in detail the elecrooptical characteristics, microscopic texture and X-ray diffraction of PS-FLC, and the effect of the polymer stabilization on the molecular alignment structure. As a result, it is guessed that two types of domain, in which there are two alignment directions monostabilized by the polymer photocured under the application of a bipolar electric field, would coexist. [ABSTRACT FROM AUTHOR]

The use of a crosslinked azobenzene liquid-crystalline polymer (CALP) system for micro-integrated actuators becomes especially attractive. CALPs can deform along the alignment direction of mesogens upon irradiation of UV/visible light owing to photochemical phase transition. In this study, to improve the bending speed, CALP films with a homogenous alignment on one surface and a homeotropic alignment on the opposite surface (hybrid alignment) were prepared and their bending behavior was investigated. The films showed photoinduced bending whose direction was determined by the surface alignment treatment, and the bending speed was greatly enhanced upon irradiation from both surfaces of the film at the same time. [ABSTRACT FROM AUTHOR]

Traditional liquid crystal alignment techniques influence mesogen alignment at the substrate alone, and rely on interactions between molecules to extend that alignment throughout a device's thickness. An alternative approach is the use of a nanostructured host that provides a large surface contact area with a guest liquid crystalline material and can extend for micrometres beyond the substrate. This permits a greater degree of control over the mesogens and allows alignment control throughout the thickness of the nanostructured host. We present the realization and experimental results using hosts fabricated through a specialized thin film process known as glancing angle deposition. [ABSTRACT FROM AUTHOR]

The electrospinning process was investigated to embed multi-walled carbon nanotubes (MWNTs) in the electrospun nanofibers of poly(methyl methacrylate) (PMMA) for anisotropic alignment and effective dispersion of carbon nanotubes in the transparent polymer substrate. The morphology of MWNT-incorporated electrospun nanofibers was substantially influenced by the types of solvent and the content of carbon nanotubes exhibiting various forms of beads, undulated fibers, or uniform fibers. In the fibrous forms of electrospun PMMA, the MWNTs were mostly attached on the surface of polymer by physical interlocking. On the other hand, when the bead-shaped PMMA was produced by the electrospinning process, most of the MWNTs were embedded in the PMMA matrix without being exposed on the polymer surfaces. Using the O2 plasma treatment for cutting-off the polymer-rich surface layer of the beads, the embedded MWNTs were exposed out of the beads and subsequently an urchin-shaped structure was obtained. The protruded MWNTs of the urchin-shaped beads could stabilize the polymer beads by the steric stabilization in the solution state and provide facile electronic pathway and percolation in the condensed solid state. [ABSTRACT FROM AUTHOR]

We studied liquid crystal (LC) alignment with ion beam (IB) on polyimide and electro-optical characteristics of twisted nematic (TN)-liquid crystal display (LCD) on the polyimide surface using obliquely ion beam (IB) exposure with new IB type equipment (DuoPIGatron type ion gun). A good uniform alignment of the nematic liquid crystal (NLC) alignment with the ion beam exposure on the polyimide surface was observed. In addition, it can be achieved the good EO properties of the ion-beam-aligned TN-LCD on polyimide surface. Also the EO characteristics of the ion-beam-aligned TN-LCD on a polyimide (PI) surface with ion beam exposure using new type IB equipment is almost the same as that of ion-beam-aligned TN-LCD on a polyimide (PI) surface with ion beam exposure using Kaufman-type Ar ion gun. [ABSTRACT FROM AUTHOR]

In this study, liquid crystal (LC) alignment effects for homeotropic alignment on the SiOx thin film by electron beam evaporation method with electron beam system and electro-optical (EO) performances of homeotropic aligned liquid crystal display (LCD) were studied. Also, the control of pretilt angles of homeotropic aligned LC on SiOx thin film as a function of thin film thickness were investigated. The uniform vertical LC alignment on the SiOx thin film surfaces with electron beam evaporation was achieved in any of the thin film thickness conditions. It is considered that the LC alignment on the SiOx thin film by electron beam evaporation is attributed to the elastic interaction between LC molecules and micro-grooves at the SiOx thin film surface created by evaporation. In addition, LC cell of the SiOx thin film by electron beam evaporation had good EO property. [ABSTRACT FROM AUTHOR]

We have investigated the static and dynamic electrooptical effects of adding an alignment layer derived from a chiral liquid crystal having SmC* and N* phases to the standard polymer alignment layer in antiferroelectric liquid crystal cells. Our results show that the added layer reduces the relaxation time of the liquid crystal, the threshold voltage and the dynamic range required to generate a full greyscale. The electrooptical response of materials was tested using a 7 level waveform, and the relaxation was studied using a novel memory test. [ABSTRACT FROM AUTHOR]

Ferroelectric copolymer of vinylide0ne fluoride and trifluoroethylene (70/30) was used as an alignment layer in nematic liquid crystal cells. The rubbed ferroelectric polymer films produce excellent planar orientation of liquid crystal molecules. We have found that the ferroelectric polymer film at one of LC cell surfaces results in strongly asymmetric electrooptical and electrical response. This fact was qualitatively explained by a model that assumes creating a “p-n” like junction between a liquid crystal and the ferroelectric polymer. [ABSTRACT FROM AUTHOR]

Copper phthalocyanine(CuPc), a widely-used semiconducting material, was deposited onto quarts substrates via a vacuum process. SEM and XRD analysis were employed to characterize the structure-controlled CuPc films. As-deposited CuPc thin films were weakly oriented according to the XRD result and were homogeneous. The conductivity of CuPc film was estimated using four-point probe measurement technique and the values of the conductivity were 8.0  ×  10 -8 – 3.5  ×  10 -7 Ω -1 cm -1 . It was observed that thermal annealing under UV irradiation could make CuPc film well-aligned since UV irradiation could participate to increase the interaction among the CuPc molecules and between the CuPc molecule and the surface of the substrate leading to closer stacking of CuPc molecules. For well-aligned CuPc thin films, the threshold voltage in I-V characteristics of the ITO/CuPc/Al device was decreased by 20%compared to as-deposited CuPc films. [ABSTRACT FROM AUTHOR]

The use of antiferroelectric liquid crystals(AFLCs)on practical applications is often precluded by their low contrast. Orthoconic AFLCs, in principle, may overcome this limitation, for they behave as isotropic plates at normal incidence. A number of orthoconic AFLC materials have been evaluated. Multiplexed seven-level driving schemes have been employed for dynamic analysis. The most relevant results include average static contrast ratio over 200:1 and dynamic contrast ratio over 130:1. On the other hand, hysteresis often shows slight voltage shifts when the cells are driven with low frequency AC signals. This feature impairs symmetry of the transmission maxima on the positive and negative lobes of the hysteresis curve. The effect is attributed to the extremely low pitch of actual orthoconic materials–usually below 1  μm. The distinctive properties of orthoconic materials make them suitable for photonic applications requiring moderate response time such as routing or beam steering applications. [ABSTRACT FROM AUTHOR]

Alignment behavior of a discotic liquid crystalline triphenylene (C8OBTP) on substrates coated with self-assembled monolayers (SAMs) of alkanethiol and asymmetrical alkyl disulfide was investigated by polarized microscopy. Discotic nematic (ND) and rectangular columnar (Colr) phases of C8OBTP shows a different alignment behavior depending on the element of SAMs. C8OBTP exhibits a fan-shaped texture on an alkanethiol SAM in Colr phase, while it has a tendency to show a planar alignment on asymmetrical alkyl disulfide SAM. The different elements of the SAM could influence the alignment behavior of discotic liquid crystal distinctly even in columnar mesophase which has highly self-cohesive forces of systems. [ABSTRACT FROM AUTHOR]

Various polymer substrates, including polyimide and polystyrene were bombarded with an Ar+ ion beam in high vacuum at an oblique angle. The alignment direction of the liquid crystal 5CB on these polymer substrates is always parallel to the ion beam propagation direction regardless of the type of polymer used. The alignment mechanism is studied using surface sensitive techniques such as Polarized Attenuated Total Reflection Infrared Spectroscopy (ATR-IR), and X-ray Photoelectron Spectroscopy. We propose that selective destruction of the weakest bonds (π bonds) in the polymer by the Ar+ ion beam results in a net excess of the remaining π bonds. The anisotropy in these π bonds align liquid crystals parallel to the ion beam propagation direction. [ABSTRACT FROM AUTHOR]

The initial stage of film formation has been analyzed using the quartz crystal microbalance (QCM) method. The resonance frequency and resistance of the QCM covered with paraffin thin film indicate that the viscoelastic properties of films can be changed even before the film formation from the melt or the solution, i.e., pre-transition phenomena can be observed. The QCM analysis also reveals that liquid crystalline molecules can be adsorbed as a solid phase in the vicinity of the interface even in the nematic liquid crystal phase. [ABSTRACT FROM AUTHOR]

We studied alignment of 5CB molecules on several surfaces by Angle Resolved X-ray Photoelectron Spectroscopy. It was found that different surfaces orient 5CB molecules with different tilt while providing qualitatively the same type of the LC alignment in the bulk. In particular, quartz and PVA gave high tilt, while NaCl and glass gave very low tilt. At the same time all these surfaces provide degenerated quasi-planar alignment in LC bulk. These results point that the orientation of LC molecules in the bulk can strongly differ from the orientation of the first adsorbed monolayer and it is determined by integral anisotropic action of the surface and interface over interface region. [ABSTRACT FROM AUTHOR]

The phase retardation of several banana type liquid crystals in their B 1 and B 2 phases is measured using a temperature controlled shear cell. In different phases the LC-cells are sheared to improve their order and the phase retardation before and after shearing is compared. It is shown that the phase retardation increases and the domain size enlarges as a result of shearing. [ABSTRACT FROM AUTHOR]

We study microscopic single domains nucleating and growing within the coexistence region of the Isotropic (I) and Nematic (N) phases of a low molecular weight liquid crystal in magnetic field. After rapidly switching on the magnetic field we measure the time needed to align the nuclei of sufficiently large size along the field. We find that this time decreases with the square of the magnetic field. When the field is removed the orientation relaxation time of an aligned domain is observed to be longer. The growth rate of nematic domains at constant temperature is found to follow the predicted power law and to increase with magnetic field. [ABSTRACT FROM AUTHOR]

We investigated experimentally the viscoelastic properties of MoS 2 nanotubes mixed with liquid crystal 8CB in the nematic phase. The MoS 2 nanotubes were dispersed with ultra-sound in ethanol and then mixed with liquid crystal; then the ethanol was evaporated. Dynamic light scattering (DLS) was used to measure the viscoelastic coefficients of the mixture in its nematic phase from the SmA-N up to the N-I phase transition. The relaxation time τ of orientational fluctuations depends on the concentration of dispersed MoS 2 nanotubes in liquid crystal, temperature and orientation of the director. By measuring the dependence of τ as a function of the scattering wave vector q, the ratio K 1 /η 1 and K 3 /η 3 were obtained ( K i - Frank elastic constants, η i - effective viscosities). Comparison of the obtained results with the values of K i /η i of pure 8CB liquid crystal shows that the ratios K 1 /η 1 and K 3 /η 3 decrease with increasing concentration of the MoS 2 nanotubes. [ABSTRACT FROM AUTHOR]

Alignment techniques for calamitic liquid crystals are well developed and play a crucial role in liquid crystal devices. Comparatively little attention has been paid to the alignment of discotic liquid crystals. Only recently the integration of discotic liquid crystals into optical and electronic devices stimulated the development of new alignment techniques for discotic nematic and columnar mesophases. This mini-review attempts a brief summary of the challenges and recent success stories. Two new approaches to the alignment of discotic columnar mesophases will also be presented. [ABSTRACT FROM AUTHOR]