Synthesis and smectogenic properties of novel phloroglucinol-based star-shaped liquid crystals containing three peripheral alkyloxylated Schiff base arms

A series of symmetrical trimeric liquid crystalline compounds of which the molecular structure with a central core of 1,3,5-benzene attached by three rod-like mesogenic Schiff base moieties via the propylene spacers and ether linkages has successfully been synthesised and characterised by infra red and nuclear magnetic resonance spectroscopic techniques. All the star-shaped compounds in this series exhibit predominantly SmC phase except the analogue possessing terminal C₈H₁₇ group. It is apparent that the members with even parity from C₁₀H₂₁ to C₁₆H₃₃ show enantiotropic SmC phase while the member with longest terminal chain of C₁₈H₃₇ is inclined to monotropic smectogen. The X-ray diffraction measurements reveal that the tilted smectic layer structures of the SmC phase are confirmed to have an obvious sharp peak at small angles of 2θ ～ 1.03°–1.48° with d-spacing values of 4.01–4.58 nm, which are corresponding to tilt angles of ～48° in the SmC phase.     

Crystallisation of nematic liquid crystal mixtures

In this paper, we propose a method to accelerate the crystallisation of nematic liquid crystal mixtures based on crystallisation theory. This method is to hold a nematic liquid crystal sample at a temperature suitable for crystal growth after aging it at a temperature suitable for nucleation. After we specified these temperatures of a nematic liquid crystal mixture using differential scanning calorimetry, we demonstrate that the two-temperature aging method is effective for the crystallisation of other nematic liquid crystal mixtures in which the crystal-liquid crystal transition temperature has so far been undetectable.     

Conductive liquid crystalline compounds having a piperazine structure

New conductive thermotropic liquid crystalline materials having a piperazine ring in the central core: 1-[4-(9-decenyloxy)phenyl]-4-alkylpiperazines (6) were synthesized. The mesomorphic behaviours of these compounds and their conductivity in the liquid crystal phase were measured. The principal features of these compounds are to exhibit a smectic B phase around room temperature (for example 6: Cr 50 SmB 81 I, °C) and to exhibit a large dark current (6d: 430 μA cm^?2, applied voltage 20 V, at 70°C) in the smectic B phase.     

Synthesis and properties of polyfluoro(silyl)acetylene nanoparticles by reaction of fluoro(silyl)acetylenes with triethylamine

Fluoro(silyl)acetylenes, which were prepared by reaction of 1,1-difluoroethylene with silyl chlorides, reacted with triethylamine to give dark-brown colored polyfluoro(silyl)acetylene powders in excellent to moderate isolated yields. In contrast, the corresponding nonfluorinated acetylene was unable to react with triethylamine at all to afford poly(silyl)acetylene under similar conditions. Polyfluoro(silyl)acetylenes thus obtained were nanometer size-controlled cubic fine particles with a good dispersibility and stability in a variety of solvents. These polyfluoro(silyl)acetylene nanoparticles exhibited clear absorption and emission spectra related to the conjugated units in polymer main chain. Furthermore, these polyfluoro(silyl)acetylene nanoparticles were applied to the surface modification of poly(methyl methacrylate) [PMMA] film to exhibit a higher oleophobicity imparted by fluorine on their surface, compared to that on the reverse side.

Synthesis and application of head-to-head-type styrene dimers bearing two fluoroalkyl end-groups

Head-to-head-type styrene and substituted styrene dimers bearing two fluoroalkyl end-groups have been efficiently synthesized by a simple reaction of perfluoroalkyl iodide with styrene under radical conditions as a mixture of meso and racemic forms. The meso form obtained from the mixture by recrystallization gave a crystal suitable for X-ray diffraction study and the crystal structure was found to be based on π-stacking of benzene rings and aggregation of fluoroalkyl chains. Dynamic light scattering measurements showed that meso-styrene dimers bearing two fluoroalkyl end-groups can form the nanometer size-controlled self-assemblies through the intermolecular π-stacking of benzene rings and aggregation of end-capped fluoroalkyl groups in methanol.

Ni‐Catalyzed [4+3+2] Cycloaddition of Ethyl Cyclopropylideneacetate and Dienynes: Scope and Mechanistic Insights

A detailed study of the Ni‐catalyzed [4+3+2] cycloaddition reaction between ethyl cyclopropylideneacetate and dienynes has been conducted, resulting in the development of a new method for the synthesis of compounds containing nine‐membered rings. We studied the reactivity of various dienynes, together with their substituent and conformational effects. The mechanism of the reaction was probed by examining the stoichiometric reactions of the Ni complexes and dienynes.     

Effects of carboxyl-group counter-ions on biodegradation behaviors of TEMPO-oxidized cellulose fibers and nanofibril films

The biodegradation behaviors of 2,2,6,6-tetramethylpiperidine-1-oxyl radical (TEMPO)-oxidized cellulose fibers (TOCs) and TEMPO-oxidized cellulose nanofibril (TOCN) films containing various carboxyl-group counter-ions were studied. Na⁺, H⁺, Ca²⁺, NH₄ ⁺, Cu²⁺, K⁺, and Cs⁺ were introduced into the TOCs or TOCN films, by ion-exchange treatment, as the carboxyl-group counter-ions. TOCs suspended in distilled water were treated with a commercial crude cellulase, and the TOCN films were subjected to soil burial tests. The crude-cellulase-treated products obtained from the TOCs were separated into water/ethanol-insoluble and -soluble fractions, i.e., high- and low-molecular-weight fractions, respectively. The degradation behaviors of the TOCs were evaluated from the weight recovery ratios of the water/ethanol-insoluble fractions and their viscosity-average degrees of polymerization. The results showed that the degradation behaviors of the TOCs were greatly influenced by the counter ion, and the counter-ion order of degradability was Na⁺ ≈ NH₄ ⁺ ≈ K⁺ ≈ Cs⁺ ? Ca²⁺ > H⁺ > Cu²⁺. These degradability differences were influenced by the swelling behavior of the corresponding TOCs in distilled water; the higher the swelling degree of the TOC, the higher the degradation efficiency of the TOC in the reaction with crude cellulase. Similar biodegradation behaviors were observed in soil burial tests for TOCN films containing various carboxyl-group counter-ions in soil burial test; again the counter ion greatly influenced the resultant biodegradability. The biodegradation behaviors of TOCs and TOCN films can therefore be controlled by selecting an appropriate carboxyl-group counter-ion.     

Three lanostane triterpenoids with antitrypanosomal activity from the fruiting body of Hexagonia tenuis

During the search for new antitrypanosomal drug leads, three new antitrypanosomal compounds, hexatenuins A–C (1–3), were isolated from the fruiting body of Hexagonia tenuis. 1 and 3 possessed an unusual malonate half-ester functional group at C-3 position, and 1 and 2 had a spirostructure in the side-chain. Their structures were elucidated using MS analyses, extensive 2D-heteronuclear NMR data interpretation. Compounds 1–3 showed in vitro antitrypanosomal activity against Trypanosoma brucei brucei with IC₅₀ values of 0.57, 8.60 and 5.62 μg/ml, respectively.     

Selective hydrogen peroxide oxidation of sulfides to sulfoxides or sulfones with MWW-type titanosilicate zeolite catalyst under organic solvent-free conditions

Selective oxidation of sulfides to sulfoxides and sulfones with hydrogen peroxide under organic solvent-free conditions was demonstrated by the MWW-type titanosilicate zeolite catalyst. Sulfides were oxidized smoothly to give sulfoxides with good selectivities at ambient temperature using 1.0–1.2 equiv of hydrogen peroxide with the MWW-type titanosilicate zeolite catalyst. Especially, the Ti-MWW with an interlayer-expanded structure (Ti-IEZ-MWW) catalyst showed high activity with good chemoselectivity for the oxidation of various sulfides. The catalyst is recyclable for at least five cycles, and the only byproduct is water. Sulfides were directly oxidized to give sulfones in high yields by 2.5 equiv of hydrogen peroxide with the MWW-type titanosilicate zeolite catalyst under organic solvent-free conditions.