Material characteristics of an active matrix LCD based upon chiral smectics

We describe the material properties of a fast switching active matrix ferroelectric liquid crystal mode. The mode relies on a monostable monodomain having a high transmission and full grey scale capability. Experimental data are compared with the results of switching model calculations and the switching mechanism is discussed. The mode is suitable for video and multimedia application and compatible with conventional amorphous silicon thin film transistors due to the small value of the spontaneous polarization.     

A new type of layer structure defects in chiral smectics

Under a low frequency AC electric field applied to the S_A phase an apparently homogeneous planar structure is obtained which is in fact composed of a system of parallel stripes perpendicular to the smectic layers. This texture persists even in the S*_C phase. The stripes are explained as a contrast on elongated focal conics originating from undulations of smectic layers. Such undulations are formed as a consequence of a reduction in the smectic layer thickness due to the electroclinic effect. The deformation of smectic layers has been calculated on the basis of the elastic free energy associated with their deformation.     

Dimerization of polar smectics A1 with a terminal cyano group in the matrix of smectics A1 of lower polarity

Binary mixtures have been studied of polar compounds with smectic A₁ phases belonging to the following series: 4-cyanobiphenyl 4-yl 4'-n-alkylbiphenyl-4-carboxylate (CBnAB) and 4-(trans-4-n-decylcyclohexyl) benzoates (10XPCHB) with X = F, NCS, COCH₃. In these systems a strong destablization of the smectic A₁ phase is observed on the side of the CBnAB component and an enhancement of the smectic A₁ phase on the side of 10XPCHB. It is shown that the anomalous behaviour of the mixtures of two A₁ smectics with a similar layer spacing is due to the dimerization of CBnAB in the matrix of 10XPCHB which is of lower polarity.     

Synthesis and chromatographic properties of an HPLC chiral stationary phase based upon human serum albumin

Summary A new HPLC stationary phase was synthesized by thein situ covalent immobilization of human serum albumin (HSA). The protein was immobilized on a commerically available diol column which had been activated with 1,1-carbonyldiimidazole. Initial chromatographic studies show that this phase can be used for chiral separations of enantiomeric solutes and that these separations may reflectin vitro binding to the HSA. The effects of mobile phase composition and temperature on the stereochemical resolutions are reported.     

Reactions of a new optically active arylperhydronaphthalenol based chiral auxiliary

(1 ,4a ,8 ,8a )-8-(5′-methoxy-2′-methylpheny])-8-methyldecahydro-1-naphthalenol is a chiral auxiliary more efficient than 8-phenylmenthol in the Diels-Alder reaction of its acrylate ester with cyclopentadiene and in the diisobutylaluminium hydride reduction of its phenylglyoxylate ester.     

Optically active dendrimers based on the planar chiral ferrocene core

The new planar chiral racemic and enantiomerically enriched Frechet-type dendrimers of the first and second generations bearing one and two branches and 1,2-disubstituted ferrocene as the core moiety were synthesized. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 6, pp. 1220–1222, June, 2008.     

Synthesis and chromatographic properties of HPLC chiral stationary phases based upon β-cyclodextrins

Chromatographia - β-cyclodextrin chiral stationary phases (CD-CSP) having different spacer lengths have been prepared and evaluated (retention, selectivity, resolution) for the liquid...     

Synthesis of novel chiral dopants based on optically active p-substituted mandelic acids

Novel esters of optically active p-substituted mandelic acids (+)-1 and (+)-2 were prepared by a convergent synthetic strategy in high enantiomeric excess (99% ee). The esters (+)-1 and (+)-2 induce helical macrostructures in the mesophases of achiral liquid-crystal materials, although neither exhibits mesorphism on its own.     

Tetrathiafulvalene based phosphino-oxazolines: a new family of redox active chiral ligands

Reaction of the lithium salt of EDT-TTF-2-(4-methyl)oxazoline with chloro-diphenylphosphine afforded the novel redox active chiral chelating ligands, EDT-TTF-phosphino-oxazolines, for which a palladium (II) dichloride complex was synthesized and structurally characterized.     

Electrostatics and the electro-optic behaviour of chiral smectics C: 'block' polarization screening of applied voltage and 'V-shaped' switching

We present a new model for the physics of thresholdless switching in chiral smectics. In the limit of high polarization, the electro-optics of chiral smectic C liquid crystals are dominated by two distinct electrostatic effects. Complete (surface to surface) 'stiffening' of the polarization field by its charge self-interaction causes the polarization to orient as a uniform block. Complete screening of applied electric field by polarization charge leads to voltage-induced orientation where the electric field in the liquid crystal is exactly zero, These effects, both operative during the 'V-shaped' portion of thresholdless transmission vs. voltage curves, combine to produce 'V-shaped' switching.     

Electrostatics and the electro-optic behaviour of chiral smectics C: 'block' polarization screening of applied voltage and 'V-shaped' switching

We present a new model for the physics of thresholdless switching in chiral smectics. In the limit of high polarization, the electro-optics of chiral smectic C liquid crystals are dominated by two distinct electrostatic effects. Complete (surface to surface) 'stiffening' of the polarization field by its charge self-interaction causes the polarization to orient as a uniform block. Complete screening of applied electric field by polarization charge leads to voltage-induced orientation where the electric field in the liquid crystal is exactly zero, These effects, both operative during the 'V-shaped' portion of thresholdless transmission vs. voltage curves, combine to produce 'V-shaped' switching.     

Template-directed synthesis of nets based upon octahemioctahedral cages that encapsulate catalytically active metalloporphyrins

meso-Tetra(N-methyl-4-pyridyl)porphine tetratosylate (TMPyP) templates the synthesis of six new metal-organic materials by the reaction of benzene-1,3,5-tricarboxylate with transition metals, five of which exhibit HKUST-1 or tbo topology (M = Fe, Mn, Co, Ni, Mg). The resulting materials, porph@MOMs, selectively encapsulate the corresponding metalloporphyrins in octahemioctahedral cages and can serve as size-selective heterogeneous catalysts for oxidation of olefins.     

Homo‐double helix formation of an optically active conjugated polymer bearing carboxy groups and amplification of the helicity upon complexation with achiral and chiral amines

An optically active, m‐terphenyl‐based π‐conjugated polymer bearing carboxy groups was synthesized by the copolymerization of the diethynyl monomer bearing a carboxy group with (S,S)‐2,5‐bis(2‐methylbutoxy)‐1,4‐dibromobenzene using Sonogashira reaction. The copolymer showed a weak circular dichroism (CD) in the main‐chain chromophore region due to a homo‐double helix formation with an excess helical handedness biased by the chiral alkoxy substituents through self‐association. However, upon complexation with achiral amines, such as piperidine, the CD intensity of the polymer significantly increased resulting in the formation of a greater excess one‐handed homo‐double helix via hydrogen‐bonded inclusion complexation with the achiral amines between each strand, leading to the amplification of the helicity. A preferred‐handed homo‐double helix was also induced in the polymer in the presence of nonracemic amines. The effect of the achiral and chiral amines on the homo‐double helix formation was investigated by comparing the CD spectra of the polymer to those of its model dimer. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2015 , 53, 990–999     

Enantioseparation characteristics of the chiral stationary phases based on natural and regenerated chitins

Natural and regenerated chitins were derivatized with 3,5‐dimethyphenyl isocyanate. The corresponding chiral stationary phases were prepared by coating the resulting chitin derivatives on 3‐aminopropyl silica gel. The swelling capacity of the chitin derivatives, enantioseparation capability, as well as eluents tolerance of the chiral stationary phases were evaluated. The results demonstrated no remarkable difference in enantioseparation capability between natural and regenerated chitins based chiral stationary phases. The similar enantioseparation characteristics of two chiral stationary phases could be understood by comparing the IR spectra of related chitin derivatives. The one of the two chiral stationary phases prepared by coating the chitin derivative with a lower molecular weight generally provided better enantioseparations. All chiral stationary phases can work in 100% chloroform, 100% ethyl acetate, 100% acetone, and the mobile phases containing a certain amount of tetrahydrofuran. The chiral stationary phase prepared from the chitin derivative with the highest swelling capacity exhibited better enantioseparations than others. This chiral stationary phase was damaged by flushing with 100% tetrahydrofuran, however, the enantioseparation capability was recovered again after the column was allowed to stand for 1 month. Furthermore, the recovered chiral stationary phase provided better enantioseparations for some chiral analytes than before.     

Carbon cloth-supported cobalt phosphide as an active matrix for constructing enzyme-based biosensor

A self-supported nanoporous cobalt phosphide (CoP) nanowire arrays on the carbon cloth (CC) as an active matrix was fabricated and utilized as an interface for the construction of hemoglobin (Hb)-based biosensors. This matrix was wrapped in a thin aluminum sheet by handmade. Moreover, the electrochemistry and electrocatalytic properties of Hb were investigated on such a matrix. The results revealed that the self-supported nanoporous CoP nanowire arrays on CC significantly enhanced the electrochemical responses of Hb. In the meantime, the immobilized Hb remained its good bioactivity and high catalytic activity to hydrogen peroxide (H₂O₂). This matrix is thus a suitable platform to develop highly sensitive enzyme-based biosensor, which has the linear range of H₂O₂ concentration from 2 to 2670 μM with a detection limit of 0.7 μM (S/N?=?3). Consequently, it is desirable to explore the possibility of developing a kind of simpler and cheaper matrix electrode.     

The effects of the bulkiness of terminal chains on the stability of smectics deduced from the crystal structures of isomeric chiral biphenyl esters

Single crystal X-ray analyses have been performed on 4'-octyloxyphenyl 4'-[(S)1-methylheptyloxy]biphenyl-4-carboxylate (8*O-O8) and 4-[( S )-1-methylheptyloxy]phenyl 4'-octyloxybipheny-4-carboxylate (8O-O8*), with the phase sequences Cr-SmC*-Ch-I and Cr-SmX-SmC*-SmA-I, respectively. Both crystals have smectic-like layer structures, in which the molecular tilt angles are 10 and 30 , respectively. In the crystal phase of 8*O-O8, biphenyl moieties are twisted probably because of steric hindrance of the bulky chiral chains linked to them, whereas in 8O-O8* they are nearly planar due to the conjugation between the alkoxy oxygen atoms and the carbonyl groups. From comparison of the properties with those of other related compounds, it is concluded that the conformation of the biphenyl moieties are closely related to the stability of smectic phases.     

Development of an N-heterocyclic carbene ligand based on concept of chiral mimetic

Development of a new N-heterocyclic carbene ligand based on the concept of a chiral mimetic is described. In Pd-catalyzed enantioselective intramolecular α-arylation of N-(2-bromophenyl)-N-methyl-2-arylpropanamide, (4R,5R)-4,5-diphenyl-1,3-diadamantylmethyl-4,5-dihydro-3H-imidazol-1-ium tetrafluoroborate is shown to function as a good N-heterocyclic carbene precursor.     

Function of an N-heterocyclic carbene ligand based on concept of chiral mimetic

Function of a new N-heterocyclic carbene ligand based on the concept of a chiral mimetic is described. With (4R,5R)-4,5-diphenyl-1,3-dialkyl-4,5-dihydro-3H-imidazol-1-ium tetrafluoroborates as N-heterocyclic carbene precursors, Rh-catalyzed enantioselective arylation (up to 27% ee) of aromatic aldehydes with arylboronic acids and Pd-catalyzed enantioselective intramolecular alpha-arylation (up to 66% ee) of N-(2-bromoaryl)-N-alkyl-2-arylpropanamides are investigated.