James A. Rego

Design and synthesis of ferroelectric liquid crystals. 15.1 FLC materials for nonlinear optics applications

Abstract We have recently reported the first FLCs designed specifically for large second order nonlinear optical (NLO) susceptibility χ(2); a series of o-nitro-1-methylheptyloxy biphenylbenzoates and phenyl biphenylcarboxylates. Properties of a stable room-temperature C* mixture of two such components (1:1 W316/W317 = MX5679) are presented. The nonlinear susceptibility, as evidenced by the Type 1 eeo deff for second harmonic generation (SHG) from 1,064 nm light for MX5679 is indeed large relative to other FLCs which have been evaluated for χ(2) (deff (ZLI3654) = 0.0016 pm/V, deff (SCE9) = 0.0037 pm/V, deff (MX5679) = 0.16 pm/V). The synthesis and some properties of second-generation FLCs designed for NLO applications is also described.

Nanoconfinement of guest materials by helical nanofilament networks of bent-core mesogens

The helical nanofilament (HNF) liquid crystal phase is a complex, hierarchical self-assembly in which bent-core molecules cooled from the isotropic melt form dense periodic arrays of nanoscale filaments of twisted smectic layers, a structure driven by an inherent tendency of the layers to be locally saddle-splayed. Here we report the results of a study of mixtures of an HNF-forming bent-core liquid crystal with a variety of organic guest molecules, showing that the high temperature, isotropic phase is completely mixed but that upon cooling the filaments form and grow, expelling the guest material from their internal volume. The nanofilaments form a network which acts as a porous nanoconfinement medium of large internal area (∼100 m2 cm−3), with the guest material confined to nanoscale interstitial volumes between the filaments. Such helical nanofilament networks represent a robust platform for potential applications in chiral separations, asymmetric synthesis, and photonic metamaterials.

Electric field induced transitions from TGBA* and TGBC* to smectic A and C states

Abstract We have observed that the application of a DC or AC field to a cell containing one of several new LCs materials in the helical smectic A (TGBA) phase (cell surfaces treated for parallel alignment) irreversibly converts the sample to a normal smectic A state in the bookshelf geometry. This observation may be due in part to a large electroclinic effect exhibited by the materials as well as the anchoring properties of the rubbed alignment layer. The threshold voltage for the field induced transition is dependent on temperature. Two different textures are observed: The TGBA shows a bright colorful texture while the induced A state shows a uniform monodomain that can be rotated into extinction between crossed polarizers. The existence of the TGBA phase for one of the new materials is confirmed in freely suspended thin films. Finally, this field induced transition may be exploited to create a novel laser-addressed LC display device.

Asymmetric synthesis of a highly soluble ‘trimeric’ analogue of the chiral nematic liquid crystal twist agent Merck S1011

The Sharpless asymmetric dihydroxylation has been utilised to synthesise a new glassy chiral dopant with large helical twisting power (β) and remarkable solubility in nematic liquid crystal hosts. Values of β range between +30.7 and +47.7 μm−1 in five different nematic hosts. A 26% mixture in E7 is homogenous indefinitely and induces a room-temperature blue phase.

Chirality Detection with FLCs—a Comment

An interesting result, with some bearing upon recently discovered unichiral LCs obtained from putatively achiral or racemic molecules, is described. Specifically, the high P ferroelectric liquid crystal W314, when prepared from racemic 2-butanol purchased from Aldrich, gave unichiral FLC samples with negative P. This was shown to be due to a slight enantiomeric excess in the Aldrich racemate; authentically racemic W314 was obtained from freshly-prepared racemic 2-butanol. These results suggest that ferroelectric electro-optic behavior is an extremely sensitive detector of net chirality in near-racemates.

Garlic (Allium sativum) Stimulates Lipopolysaccharide-induced Tumor Necrosis Factor-alpha Production from J774A.1 Murine Macrophages

Garlic (Allium sativum) is known to have many beneficial attributes such as antimicrobial, antiatherosclerotic, antitumorigenetic, and immunomodulatory properties. In the present study, we investigated the effects of an aqueous garlic extract on macrophage cytokine production by challenging the macrophage J774A.1 cell line with the garlic extract in the absence or presence of lipopolysaccharide (LPS) under different conditions. The effect of allicin, the major component of crushed garlic, was also investigated. Using enzyme‐linked immunosorbent assay and reverse transcriptase‐quantitative polymerase chain reaction, it was found that garlic and synthetic allicin greatly stimulated tumor necrosis factor‐alpha (TNF‐α) production in macrophages treated with LPS. The TNF‐α secretion levels peaked earlier and were sustained for a longer time in cells treated with garlic and LPS compared with cells treated with LPS alone. Garlic acted in a time‐dependent manner. We suggest that garlic, at least partially via its allicin component, acts downstream from LPS to stimulate macrophage TNF‐α secretion.

Ferroelectric and antiferroelectric odd–even behavior in a tricarbosilane-terminated liquid crystal homologous series

A new class of polyphilic mesogens composed of a tolanphenyl carboxylate core, a chiral alkoxy tail, and a tricarbosilane terminated alkoxy tail was synthesized, and shown to self-organize into nanophase segregated, smectic liquid crystalline (LC) phases. It was found that the number of carbons in the alkyl spacer between the tricarbosilane and the core controlled the observed phase with perfect fidelity: odd-carbon spacers gave antiferroelectric phases, and even-carbon spacers gave ferroelectric phases. Even more interestingly, homologues with odd carbon number show the rare and useful chiral orthoconic antiferroelectric SmCA* phase, where the optic axis tilt alternates from layer to layer between +45° and −45°, making the molecular directors in adjacent layers orthogonal. The even-carbon homologues exhibit the SmC* phase with close to 45° tilt. The findings demonstrate that the supramolecular self-organization of polyphilic mesogens may be controlled by the length of hydrocarbon spacers.

Design and synthesis of ferroelectric liquid crystals. 22. side-by-side dimers for nonlinear optics

Abstract Possessing excellent processibility on silicon integrated circuits and a thermodynamically stable polar supermolecular structure, chiral smectic C (C*) ferroelectric liquid crystals (FLCs) are promising materials for use in ultra-fast (>500 MHz) integrated electro-optic modulators. In order to realize this promise, however, it is necessary to obtain FLC materials with values of the electronic second order nonlinear optical (NLO) susceptibility χ(2) larger than have been reported to date. One way to achieve this goal is to obtain orientation of “large β” organic functional arrays, composed of two rings with a conjugating spacer unit, along the polar axis in the C* phase. Such long molecular groupings, however, typically orient along the director in LC phases, normal to the C* polar axis. We present herein the results of the initial investigation of an approach for achieving large χ(2) in FLCs. In this case orientation of the prototypical large β chromophore found in the dye Disperse Red 1 (DR1) is...

Investigation of Allicin Stability in Aqueous Garlic Extract by High Performance Liquid Chromatography Method

Aims: The aims of this work were to quantify allicin an abundant antioxidant in different aqueous garlic extract samples and to determine the stability of allicin in the extract under different thermal and solvation conditions. Study Design: Descriptive research. Place and Duration of Study: Department of Chemistry and Biochemistry and Department of Biological Sciences, California State Polytechnic University, Pomona, between May 2013 and September 2014. Original Research Article Chong et al.; JSRR, 4(7): 590-598, 2015; Article no.JSRR.2015.062 591 Methodology: A reversed-phase high performance liquid chromatography method was used to analyze allicin in garlic extracts. Quantification of allicin in garlic extracts was made by comparing its peak area with the standard calibration curve of allicin with known concentrations. The kinetic study of allicin degradation in garlic extracts was based on the Arrhenius theory. Results: The amount of allicin in aqueous garlic extracts varied from 35.6 to 44.5 mM. The thermal stability study shows that the degradation of allicin is a first-order reaction and the preliminary data shows that the degradation of allicin in different solvents has different kinetic parameters. Conclusion: The concentration of allicin in garlic extract samples was similar to each other, despite of different sampling dates. For medicinal purpose, garlic extracts should be used freshly to prevent any degradation of allicin.