Thermotropic copolyesters. III. Synthesis and characterization of liquid crystal copolyesters containing the bicyclo[2.2.2]octane ring system

A number of thermotropic copolyesters which contain the bicylo[2.2.2]octane ring system have been synthesized. Because of the stiffening effect of the bicyclo[2.2.2]octane group on the chain, the sebacoyl spacer was used to obtain meltable compositions.     

Synthesis and X-Ray Crystal Structure Study of ]2-Methyl-4-(2-methylbenzoyl)-phenoxy] Acetic Acid Hydrazide

Benzophenone analog 3 has been synthesized and characterized by the X-ray diffraction (XRD) method. The compound crystallizes in a monoclinic space group P2₁/c with cell parameters a = 7.701(8) Å, b = 7.151(5) Å, c= 28.323(3) Å, = 104.639(4)°, Z = 4. The structure exhibits intra- and intermolecular hydrogen bonding of the type N–HO, C–HO, and N–HN. The molecules are interlinked through hydrogen bonds forming an infinite chain. This polymeric-like structure may play an important role in biological activity.     

Influence of chain architecture on phase behaviour of styrene-(styrene/butadiene)-styrene triblock copolymers and their binary blends

The phase behaviour of symmetric (LN4) and asymmetric (LN3) triblock copolymers based on styrene-b-(styrene-co-butadiene)-b-styrene (S-SB-S) and their blends have been studied using transmission electron microscopy (TEM) and small-angle X-ray scattering (SAXS) and were correlated with rheological properties. A direct control over the final morphology and segregation strength for the block copolymer blends was achieved by blending of LN3 and LN4. The interaction parameter (χ) for LN4 is extracted by fitting the SAXS patterns at temperatures well above the ODT in consistency with Leibler mean-field structure-function for ABA triblock copolymers. A weak temperature dependency of χ has been observed which revealed that the phase behaviour in LN4 is mainly controlled by the entropic term. In the low frequency regime a non-terminal flow behaviour was observed in LN3 revealing the persistence of ordered structure within the experimental temperature range whereas a terminal flow behaviour with composition fluctuation was observed in LN4. G′ vs. G″ plots indicated a solid-like elastic melt behaviour for LN3 whereas presence of ODT over a broad temperature range was observed for LN4. ODT is observed to increase non-linearly with increase in LN3 content in the blends. ODT behaviour of the blends further reveals that the blends shift from weak-segregation to intermediate-segregation strength with the increase in LN3 content. The improvement in the state of ordering along with the change in morphology with the increase of LN3 content is attributed to co-surfactant effect between the PS end-blocks of LN3 and LN4 inside PS-rich phase.     

Studies on ion-pair and triple-ion formation of some tetraalkylammonium salts in binary solvent mixtures of benzene and tetrahydrofuran at 298.15 K

Conductivities of some tetraalkylammonium halides, viz. tetrabutylammonium bromide (Bu₄NBr), tetrapentylammonium bromide (Pen₄NBr), tetrahexylammonium bromide (Hex₄NBr) and tetraheptylammonium bromide (Hep₄NBr) were measured at 298.15 K in THF + C₆H₆ mixtures with 10, 20, 30 and 40 mass% of C₆H₆. A minimum in the conductance values was observed as concentration increases, which dependent both on the salt and the solvent. The observed molar conductivities were explained by the formation of ion-pairs (M⁺ + X⁻ ↔ MX, K_P) and triple-ions (2 M⁺ + X⁻ ↔ M₂X⁺; M⁺ + 2X⁻ ↔ MX₂⁻, K_T). A linear relationship between the triple-ion formation constants [log(K_T/K_P)] and the salt concentrations at the minimum conductivity (log C_min) was given for all salts in C₆H₆ + THF mixtures. The formation of triple-ions might be attributed to the ion sizes in solutions in which coulombic interactions and covalent bonding forces act as the main forces between the ions (R₄N⁺ X⁻).     

Field emission investigation of single Fe-doped SnO2 wire

Tin oxide submicronwires doped with Fe element were prepared by the thermal evaporation method. Morphological and structural characterizations revealed wires with sub micron size and crystalline in nature. The field electron emission from the single Fe:SnO₂ wire was carried out in conventional field emission microscope. The Fowler–Nordheim plot obtained from I–V characteristics of the wire showed a linear behavior typical that of metal. The field enhancement factor estimated from the slope of the F–N plot is 7455 cm^?1, indicating that the field emission is from nanometric features of the emitter. A current density of 10 A/cm² has been obtained at an applied field of 4.845 × 10³ V/μm. The field emission current–time record at a current level of 1 μA for more than 3 h duration is promising for various field emissions based applications.     

Vibrational Dynamics,Phonon Dispersion and Specific Heat in Gas Permeable Poly(4-Methyl-2-Pentyne)

Poly(4-methyl-2-pentyne) (PMP) is an amorphous glassy disubstituted acetylene based polymer. The excellent gas-separation and mechanical properties of these polymers have stipulated their use as membrane material for vapor and gas separation. PMP is among the hydrocarbon disubstituted polyacetylenes which have been synthesized to date. This polymer combines excellent gas and vapor permeability with good resistance to organic solvents. As was shown recently, PMP offers promise in the manufacture of nanocomposite membranes for the separation of various hydrocarbon mixtures. It is also of importance as its monomer, 4-methyl- 2-pentyne, can be easily derived from commercial compounds, 4-methyl-2-pentene or methyl isobutyl ketone, produced on a large scale. It is known that PMP exists in cis and trans configurations. Synthetic conditions, e.g., the used catalyst, temperature, solvent etc., of substituted polyacetylenes decide percentage of different configurations (cis or trans). Different geometries of macromolecules can influence the supramolecular structure of the polymer, which primarily defines its properties, such as solubility, permeability, sorption, etc. Qualitative assignments of few bands of IR spectra are reported earlier. We present here, complete normal mode analysis and dispersion curves for PMP using Wilson GF matrix method modified by Higgs using Urey-Bradley force field. Dispersion curves for PMP are drawn and salient features are discussed. Predicted values of specific heat via density-of-states are also reported.     

Quantitative evaluation of benzene, toluene, and xylene in the larvae of Drosophila melanogaster by solid-phase microextraction/gas chromatography/mass spectrometry for potential use in toxicological studies

A simple, rapid, and solvent-free method for quantitative determination of benzene, toluene, and Xylene in exposed Drosophila larvae was developed using headspace solid-phase microextraction (HS-SPME) coupled to GC/MS. Larvae fed on standard Drosophila food mixed with benzene, toluene, and Xylene for 48 h were homogenized in Milli-Q water. Extraction of benzene, toluene, and Xylene was performed at 65 degrees C for 30 min on the SPME fiber (silica-fused). Subsequently, the fiber was desorbed in the GC injection port, followed by GC/MS analysis in the selected-ion monitoring mode. An external calibration curve was used for the quantification of benzene, toluene, and Xylene in the exposed organism. Recoveries were in the range of 78-82% (intraday) and 76-81% (interday) in larvae, and 91-96% (intraday) and 87-92% (interday) in the diet. LOD with an S/N of 3:1 and LOQ with an S/N of 10:1 were in the range of 0.01-0.023 and 0.034-0.077 microg/L, respectively. Percent RSD values for benzene, toluene, and Xylene were in the range of 0.50-0.81 (intraday) and 0.89-1.23 (interday) for retention time, and 2.16--3.85 (intraday) and 2.99-4.95 (interday) for peak concentration, showing good repeatability. This method was sensitive enough to quantitate benzene, toluene, and Xylene in small exposed organisms like Drosophila larvae. The SPME/GC/MS method developed may have wider applications in various in vivo toxicological studies.     

Artabotryols A – E,New Lanostane Triterpenes from the Seeds of Artabotrys odoratissimus

Six new lanostane triterpenes, artabotryols A, B, C1, C2, D, and E ( 1, 2, 3a, 3b, 4 , and 5 , resp.) have been isolated from the seeds of Artabotrys odoratissimus (Annonaceae). Their structures have been established as (3α,22S,25R)‐3‐hydroxy‐22,26‐epoxylanost‐8‐en‐26‐one ( 1 ), (3α,22S,25R)‐22,26‐epoxylanost‐8‐ene‐3,26‐diol ( 2 ), (3α,22S,25R,26R)‐26‐methoxy‐22,26‐epoxylanost‐8‐en‐3‐ol ( 3a ), (3α,22S,25R, 26S)‐26‐methoxy‐22,26‐epoxylanost‐8‐en‐3‐ol ( 3b ), (3α,22S,25R)‐3,22‐dihydroxylanost‐8‐en‐26‐oic acid ( 4 ) and (3α,7α,11α,22S,25R)‐3,7,11‐trihydroxy‐22,26‐epoxylanost‐8‐en‐26‐one ( 5 ) by spectroscopic studies and chemical correlations.     

An efficient synthetic approach to novel nickel(II) 2‐benzazolo‐5,10,15,20‐tetraphenylporphyrins

A simple and efficient synthesis of nickel(II) 2‐benzazolo‐5,10,15,20‐tetraphenylporphyrins from nickel(II) 2‐formyl‐5,10,15,20‐tetraphenylporphyrin and o‐arylenediamines, o‐aminophenols or o‐aminothiophenol in 1,2‐dichlorobenzene is described. A diverse range of novel β‐substituted azoloporphyrins has been successfully synthesized in good yields and their structures are confirmed on the basis of spectral data. J. Heterocyclic Chem., (2012).     

Sulfuric acid-functionalized mesoporous benzene-silica with a molecular-scale periodicity in the walls

Novel sulfuric acid-functionalized mesoporous benzene-silicas with a molecular-scale periodicity in the walls were derived from the mesoporous benzene-silica possessing mercaptopropyl groups by the oxidative transformation of -SH into -SO3H.