Exploring the Impact of Linkage Structure in Ferroelectric Nematic and Smectic Liquid Crystals.

The liquid crystal molecule 3-fluoro-4-(3,4,5-trifluorophenyl)phenyl 2,6-difluoro-4-(trans-5-n-propyl-1,3-dioxane-2-yl)benzoate (DIO) has attracted considerable interest owing to its unique ferroelectric nematic phase and extraordinarily high dielectric constant. To expand the DIO series, novel analogs with 1,3-dioxane units converted to ester units (EST analogs) were synthesized, and their physical properties were characterized. The EST analogs exhibited ferroelectric phases similar to those of the corresponding DIO analogs. Interestingly, an EST analogue featuring a defluorinated benzoate unit exhibited a ferroelectric smectic A phase, despite its smaller longitudinal dipole moment of 6.9 D. This result diverges from the common knowledge that the formation of large longitudinal dipoles is traditionally effective in the emergence of ferroelectric phases. Unlike the DIO series, the EST analogs can be readily obtained without the formation of undesired geometric isomers, which is advantageous for practical applications. The results of this study provide valuable insights into the design of liquid-crystalline materials expressing ferroelectric phases.

Fluid Layered Ferroelectrics with Global C∞v Symmetry.

Ferroelectricity in fluid materials, which allows free rotation of molecules, is an unusual phenomenon raising cutting-edge questions in science. Conventional ferroelectric liquid crystals have been found in phases with low symmetry that permit the presence of spontaneous polarization. Recently, the discovery of ferroelectricity with high symmetry in the nematic phase has attracted considerable attention. However, the physical mechanism and molecular origin of ferroelectricity are poorly understood and a large domain of macroscopically oriented spontaneous polarization is difficult to fabricate in the ferroelectric nematic phase. This study reports new fluid layered ferroelectrics with the C∞v symmetry in which nearly complete orientation of the spontaneous polarization remains stable under zero electric field without any orientation treatment. These ferroelectrics are obtained by simplifying the molecular structure of a compound with a known ferroelectric nematic phase, although the simplification reduced the dipole moment. The results provide useful insights into the mechanism of ferroelectricity due to dipole-dipole interactions in molecular assemblies. The new ferroelectric materials are promising for a wide range of applications as soft ferroelectrics.

Ultraviolet light screen using cholesteric liquid crystal capsules on the basis of selective reflection.

Sunscreen can protect human skin from sunlight by decreasing exposure to ultraviolet (UV) light, specifically UV-B and UV-A. In this study, a new type of UV screen system is proposed using cholesteric liquid crystal (CLC) capable of selectively reflecting UV-A within the human skin temperature range of 32-36 °C. Polycaprolactone (PCL) capsules with CLC mixture which had a helical chiral pitch corresponding to the wavelength of UV light were made by a solvent evaporation method. The average diameter of the capsules was about 34 µm. Consequently, it was confirmed that the CLC mixture (COC : CN = 80 : 20) could reflect UV-A light over 350-380 nm within the human skin temperature range. Also, it was confirmed that the CLC/PCL microcapsules could block UV light over 290-400 nm by about 6%.

High-Performance Polymer Dispersed Liquid Crystal Enabled by Uniquely Designed Acrylate Monomer.

The widespread electro-optical applications of polymer dispersed liquid crystals (PDLCs) are hampered by their high-driving voltage. Attempts to fabricate PDLC devices with low driving voltage sacrifice other desirable features of PDLCs. There is thus a clear need to develop a method to reduce the driving voltage without diminishing other revolutionary features of PDLCs. Herein, we report a low-voltage driven PDLC system achieved through an elegantly simple and uniquely designed acrylate monomer (A3DA) featuring a benzene moiety with a dodecyl terminal chain. The PDLC films were fabricated by the photopolymerization of mono- and di-functional acrylate monomers (19.2 wt%) mixed in a nematic liquid crystal E7 (80 wt%). The PDLC film with A3DA exhibited an abrupt decline of driving voltage by 75% (0.55 V/µm) with a high contrast ratio (16.82) while maintaining other electro-optical properties almost the same as the reference cell. The response time was adjusted to satisfactory by tuning the monomer concentration while maintaining the voltage significantly low (3 ms for a voltage of 0.98 V/µm). Confocal laser scanning microscopy confirmed the polyhedral foam texture morphology with an average mesh size of approximately 2.6 µm, which is less in comparison with the mesh size of reference PDLC (3.4 µm), yet the A3DA-PDLC showed low switching voltage. Thus, the promoted electro-optical properties are believed to be originated from the unique polymer networks formed by A3DA and its weak anchoring behavior on LCs. The present system with such a huge reduction in driving voltage and enhanced electro-optical performance opens up an excellent way for abundant perspective applications of PDLCs.

Substituent effects of bridged binaphthyl-type chiral dopants on the helical twisting power in dopant-induced chiral liquid crystals.

A new series of chiral dopants, (R)-6,6'-halogenated (1b-1e, X = F, Cl, Br and I) and -methylated (1f) binaphthyl compounds, were designed and synthesized to create chiral liquid crystals by doping them into an achiral nematic liquid crystal (NLC). The influence of halogen (X = F, Cl, Br and I) and methyl substituent factors, such as steric, polar, and polarizability properties, on the helical twisting power (HTP) and their temperature dependences on the chiral dopants were investigated in two host NLCs with different characteristics, fluorinated JC-1041XX and N-(4-methoxybenzylidene)-4-butylaniline (MBBA). The chiral dopants possessing less steric and larger polarizability factors increased the HTP values. The structural similarity and electrostatic arene-arene interactions between the chiral dopants and the NLC molecules also exerted important influences on these values. The temperature dependence of the HTP (HTPt.d.) values also correlated well with the steric and polarizability substituents factors in the two host NLCs. Their correlation coefficients (R 2) depended on the molecular structural similarity between the chiral dopant and the NLC.

Reversible Broad-Spectrum Control of Selective Reflections of Chiral Nematic Phases by Closed-/Open-Type Axially Chiral Azo Dopants.

Invited for this month's cover picture is the groups of Professor Hirotsugu Kikuchi and Dr. Yasushi Okumura at the Institute for Materials Chemistry and Engineering at Kyushu University (Japan). External dynamic control of molecular self-organized superstructures with unique features has been researched, as these structures are applicable to chiral molecular devices. The cover picture shows photocontrol of selective reflection color that originated from the self-organized helical structure of chiral nematic liquid crystals (N*LCs) using closed-/open-type dopants. The drastic structure changes of the dopants by light stimuli enable reversible broad-spectrum control of selective reflections of N*LCs with opposite helical sign. Read the full text of the Full Paper at 10.1002/open.201700121.

Reversible Broad-Spectrum Control of Selective Reflections of Chiral Nematic Phases by Closed-/Open-Type Axially Chiral Azo Dopants.

We demonstrate reversible RGB-color photocontrol of a chiral nematic liquid crystal (N*LC) by using newly synthesized closed- and open-type chiral dopants. The photoswitching elements in the dopants are azobenzene units on axially chiral binaphthyl cores. Owing to cis-trans photoisomerization of the azobenzene units, both closed- and open-type compounds showed higher solubility, larger helical twisting power (HTP), and larger changes in HTP than conventional chiral dopants in host LCs. Thus, even at very low dopant concentrations, we successfully controlled the chirality of the induced helical structure of the N*LCs. Consequently, the N*LCs reflected right- and left-handed circularly polarized light (CPL) under a light stimulus. In the N*LCs with closed-type chiral dopants, the RGB-color reflection was reversibly controlled within several seconds. Interestingly, the open-type chiral dopant reversibly inverted CPL with opposite handedness in the near and short-wave IR regions. These novel materials are expected to realize new applications and perspectives in color information and similar technologies.

A Fluid Liquid-Crystal Material with Highly Polar Order.

An anomalously large dielectric permittivity of ≈104 is found in the mesophase temperature range (MP phase) wherein high fluidity is observed for a liquid-crystal compound having a 1,3-dioxane unit in the mesogenic core (DIO). In this temperature range, no sharp X-ray diffraction peak is observed at both small and wide Bragg angles, similar to that for a nematic phase; however, an inhomogeneous sandy texture or broken Schlieren one is observed via polarizing optical microscopy, unlike that for a conventional nematic phase. DIO exhibits polarization switching with a large polarization value, i.e., P = 4.4 µC cm-2 , and a parallelogram-shaped polarization-electric field hysteresis loop in the MP phase. The inhomogeneously aligned DIO in the absence of an electric field adopts a uniform orientation along an applied electric field when field-induced polarization switching occurs. Furthermore, sufficiently larger second-harmonic generation is observed for DIO in the MP phase. Second-harmonic-generation interferometry clearly shows that the sense of polarization is inverted when the +/- sign of the applied electric field in MP is reversed. These results suggest that a unidirectional, ferroelectric-like parallel polar arrangement of the molecules is generated along the director in the MP phase.

Hierarchical spatial heterogeneity in liquid crystals composed of graphene oxides.

Graphene oxide (GO) is a class of two-dimensional materials with a thickness of about 1 nm and a broad distribution of lateral dimension commonly approaching several micrometers. A dispersion of GOs in water often forms a liquid crystal, which is expected to be a promising precursor for the fabrication of carbon-based materials with well-ordered structures. To accelerate the application of GO-based liquid crystals, their structures and physical properties at various sizes must be well understood. To that end, we examined the local rheological properties of GO-based liquid crystals in the nematic phase using a particle tracking technique, where local properties can be accessed by observing the thermal motion of embedded probe particles. Particle diffusion was spatially heterogeneous, and depended on the size of the particles. Such a size-dependent heterogeneity can be associated with a hierarchical local environment, which is time-dependent for this system. The anisotropic particle diffusion originated from particles trapped in between the GO layers and in isotropic-like regions. The aggregation states of the GO dispersion composed of nematic and isotropic-like regions were observed using confocal laser scanning microscopy.

Volume Phase Transitions of Slide-Ring Gels.

The volume phase transition of slide-ring gels with freely-movable cross-linking junctions was investigated. Ionic chemical gels with fixed cross-linking junctions undergo volume phase transitions when they have higher than the critical degree of ionization. However, the experimentally-observed critical ionization value for slide-ring gels is much higher than theoretical values for chemical gels. This difference indicates that the volume phase transition is significantly suppressed in slide-ring gels. The mesoscale structure at various swollen or shrunken states was also investigated by small angle X-ray scattering. Changes in the scattering patterns with shrinking slide-ring gels suggest microphase separation due to the sliding of cyclic molecules threaded along the axis of the polymer chains, which may suppress the volume phase transition. In addition, slide-ring gels absorbed/desorbed greater than equilibrium volumes in the shrinking/swelling processes and showed slow dynamics; these observations are also related to their sliding properties.

Recombinant Fusion Allergens, Cry j 1 and Cry j 2 from Japanese Cedar Pollen, Conjugated with Polyethylene Glycol Potentiate the Attenuation of Cry j 1-Specific IgE Production in Cry j 1-Sensitized Mice and Japanese Cedar Pollen Allergen-Sensitized Monkeys.

BACKGROUND: Japanese cedar (Cryptomeria japonica) pollinosis is the most prevalent seasonal rhinitis in Japan. A standardized Japanese cedar pollen extract (CPE) containing 1.5-4.2 µg of Cry j 1 is currently the highest-concentration extract available for allergen-specific immunotherapy (SIT) against this pollinosis. Therefore, we developed a PEGylated fusion protein as a more effective SIT vaccine against Japanese cedar pollinosis. METHODS: The fusion protein of major allergens for Japanese cedar pollen, Cry j 1 and Cry j 2, was expressed in Escherichia coli and conjugated with polyethylene glycol (PEG). The purified PEGylated Cry j 1/2 fusion protein (PEG-fusion) was subcutaneously injected four times into Cry j 1- sensitized mice and CPE-sensitized monkeys. The mice were then subcutaneously challenged with Cry j 1 and serum levels of Cry j 1-specific immunoglobulin, and the proliferation and cytokine production of splenocytes were analyzed. The monkeys were intranasally challenged with CPE and analyzed for Cry j 1-specific immunoglobulin levels in plasma. RESULTS: Cry j 1-specific IgE was significantly attenuated in the PEG-fusion-treated group after Cry j 1-challenge and Cry j 1-specific IgG was significantly increased following PEG-fusion treatment in mice and monkeys. Proliferation and Th2-type cytokine production in splenocytes stimulated with Cry j 1 were also reduced in PEG-fusion-treated mice. IL10 and IL2 production were reduced, but not significantly, while IFN-x03B3; was significantly increased in the PEG-fusion-treated group. CONCLUSIONS: A high-dose injection of PEG-fusion appears to be a valid candidate for a safer and more effective vaccine than the conventional SIT extract for Japanese cedar pollinosis.

Photo-Induced Anomalous Deformation of Poly(N-Isopropylacrylamide) Gel Hybridized with an Inorganic Nanosheet Liquid Crystal Aligned by Electric Field.

Poly-(N-isopropylacrylamide) (PNIPA) hydrogel films doped with uniaxially aligned liquid crystalline (LC) nanosheets adsorbed with a dye are synthesized and its anomalous photothermal deformation is demonstrated. The alignment of the nanosheet LC at the cm-scale is easily achieved by the application of an in-plane or out-of-plane AC electric field during photo-polymerization. A photoresponsive pattern is printable onto the gel with µm-scale resolution by adsorption of the dye through a pattern-holed silicone rubber. When the gel is irradiated with light, only the colored part is photothermally deformed. Interestingly, the photo-irradiated gel shows temporal expansion along one direction followed by anisotropic shrinkage, which is an anomalous behavior for a conventional PNIPA gel.

Low-temperature properties of polymer-stabilised liquid-crystal blue phases.

The temperature dependences of the Kerr coefficient and the response time in the electrooptical effect of polymer-stabilised blue phases (PSBPs) of liquid crystals (LCs) with various polymer concentrations are investigated in a wide temperature range including temperatures lower than room temperature. The Kerr coefficients are found to abruptly decrease at low temperature, and the response time-temperature relation obeys the Arrhenius equation. For comparison of the Kerr effect and molecular rotation at low temperature, various physical properties such as permittivity, rotational relaxation time and dielectric relaxation strength of the PSBPs are investigated. The electrooptical response times and the dielectric relaxation times show different temperature dependences, and rotation of LC molecules in PSBPs was sufficiently active at low temperature and not strongly affected by the polymer.

Tuning the stability of CaCO3 crystals with magnesium ions for the formation of aragonite thin films on organic polymer templates.

Thin-film growth of aragonite CaCO3 on annealed poly(vinyl alcohol) (PVA) matrices is induced by adding Mg(2+) into a supersaturated solution of CaCO3. Both the growth rate and surface morphology of the aragonite thin films depend upon the concentration of Mg(2+) in the mineralization solution. In the absence of PVA matrices, no thin films are formed, despite the presence of Mg(2+). Molecular dynamics simulation of the CaCO3 precursor suggests that the transition of amorphous calcium carbonate to crystals is suppressed in the presence of Mg(2+). The role for ionic additives in the crystallization of CaCO3 on organic templates obtained in this study may provide useful information for the development of functional hybrid materials.

NMR study on the major mite allergen Der f 2: its refined tertiary structure, epitopes for monoclonal antibodies and characteristics shared by ML protein group members.

Group 2 major mite allergens Der f 2 and Der p 2 are classified into the recently identified group of MD-2-related lipid-recognition (ML) proteins, but the ligands and biological functions of these allergens are unknown. We have obtained a high-quality NMR structure for Der f 2, and found that it is more similar to the crystal structure of NPC2, a distant homologue, than to that of Der p 2, in terms of the separation and angle between the two major beta-sheets. This made us propose that ML proteins undergo clamshell-like motions that change the sizes of ligand-binding spaces inside their immunoglobulin-fold beta-sandwich to accommodate lipid molecules. This type of motion in lipopolysaccaride recognition of MD-2 is suggested to be likely as well by structural models. We also report the applicability of NMR differential exchange broadening experiments for complexes of intact monoclonal antibodies and antigens; using this technique, we have detected the conformational epitopes for monoclonal antibodies 15E11 and 13A4 as two separate surface patches.

Crystallization and preliminary X-ray analysis of Der f 2, a potent allergen derived from the house dust mite (Dermatophagoides farinae).

Although a number of allergens have been identified and isolated, the underlying molecular basis for the potent immune response is poorly understood. House dust mites (Dermatophagoides sp.) are ubiquitous contributors to atopy in developed countries. The rhinitis, dermatitis and asthma associated with allergic reactions to these arthropods are frequently caused by relatively small (125-129 amino acids) mite proteins of unknown biological function. Der f 2, a major allergen from the mite D. farinae, has been recombinantly expressed, characterized and crystallized. The crystals belong to the tetragonal space group I4(1)22, with unit-cell parameters a = b = 95.2, c = 103.3 A. An essentially complete (97.2%) data set has been collected to 2.4 A at a synchrotron source. Attempts to solve the crystal structure of Der f 2 by molecular replacement using the NMR coordinates for either Der f 2 or Der p 2 (the homologous protein from D. pteronyssinus) failed, but preliminary searches using the crystalline Der p 2 atomic coordinates appear to be promising.

A glutamine synthetase mutant of Saccharomyces cerevisiae shows defect in cell wall.

To study the organization and biosynthesis of the yeast cell wall, hypo-osmolarity-sensitive mutants of Saccharomyces cerevisiae were analyzed. Cells of JS4 were irregular in shape and fragile. Calcofluor staining and quantitative analysis indicated that the chitin content was reduced. By DNA cloning and genetic analysis, the mutation hpo1-1 was found to be allelic to GLN1 which encodes glutamine synthetase. The glutamine content was significantly low in JS4, and the mutant was recovered from the cell wall defect by supplying glutamine in the medium. Partial inhibition of glutamine synthetase by phosphinothricin also induced defects in the cell wall. These results indicate that the shortage of glutamine affects cell wall integrity prior to other cellular functions.