3-Ethyl-4-methyl-1H-pyrazol-2-ium-5-olate

The title compound, C(6)H(10)N(2)O, is a zwitterionic pyrazole derivative. The crystal packing is predominantly governed by a three-center iminium-amine N(+)-H center dot center dot center dot O(-)center dot center dot center dot H-N interaction, leading to an undulating sheet-like structure lying parallel to (100).

Ethyl 6-methyl-2-sulfanylidene-4-[4(trifluoromethyl)phenyl]-1,2,3,4-tetrahyd ropyrimidine-5-carboxylate

The title compound, C(15)H(15)F(3)N(2)O(2)S, adopts a conformation with an intramolecular C-H center dot center dot center dot pi interaction. The dihedral angles between the planes of the 4-(trifluoromethyl) phenyl and ester groups with the plane of the six-membered tetrahydropyrimidine ring are 81.8 (1) and 16.0 (1)degrees, respectively. In the crystal structure, intermolecular N-H center dot center dot center dot S hydrogen bonds link pairs of molecules into dimers and N-H center dot center dot center dot O interactions generate hydrogen-bonded molecular chains along the crystallographic a axis.

Chitosan-polyvinyl alcohol-sulfonated polyethersulfone mixed-matrix membranes as methanol-barrier electrolytes for DMFCs

Chitosan (CS)-polyvinyl alcohol (PVA) cross-linked with sulfosuccinic acid (SSA) and modified with sulfonated polyethersulfone (SPES) mixed-matrix membranes are reported for their application in direct methanol fuel cells (DMFCs). Polyethersulfone (PES) is sulfonated by chlorosulfonic acid and factors affecting the sulfonation reaction, such as time and temperature, are studied. The ion-exchange capacity, degree of sulfonation, sorption, and proton conductivity for the mixed-matrix membranes are investigated. The mixed-matrix membranes are also characterised for their mechanical and thermal properties. The methanol-crossover flux across the mixed-matrix membranes is studied by measuring the mass balance of methanol using the density meter. The methanol cross-over for these membranes is found to be about 33% lower in relation to Nafion-117 membrane. The DMFC employing CS-PVA-SPES mixed-matrix membrane with an optimum content of 25 wt % SPES delivers a peak power-density of 5.5 mW cm-2 at a load current-density of 25 mA cm-2 while operating at 70 degrees C. (C) 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012

Structural Transformations, Composition Anomalies and a Dramatic Collapse of Linear Polymer Chains in Dilute Ethanol-Water Mixtures

Water-ethanol mixtures exhibit many interesting anomalies, such as negative excess partial molar volume of ethanol, excess sound absorption coefficient at low concentrations, and positive deviation from Raoult's law for vapor pressure, to mention a few. These anomalies have been attributed to different, often contradictory origins, but a quantitative understanding is still lacking. We show by computer simulation and theoretical analyses that these anomalies arise from the sudden emergence of a bicontinuous phase that occurs at a relatively low ethanol concentration of x(eth) approximate to 0.06-0.10 (that amounts to a volume fraction of 0.17-0.26, which is a significant range!). The bicontinuous phase is formed by aggregation of ethanol molecules, resulting in a weak phase transition whose nature is elucidated. We find that the microheterogeneous structure of the mixture gives rise to a pronounced nonmonotonic composition dependence of local compressibility and nonmonotonic dependence in the peak value of the radial distribution function of ethyl groups. A multidimensional free energy surface of pair association is shown to provide a molecular explanation of the known negative excess partial volume of ethanol in terms of parallel orientation and hence better packing of the ethyl groups in the mixture due to hydrophobic interactions. The energy distribution of the ethanol molecules indicates additional energy decay channels that explain the excess sound attenuation coefficient in aqueous alcohol mixtures. We studied the dependence of the solvation of a linear polymer chain on the composition of the water-ethanol solvent. We find that there is a sudden collapse of the polymer at x(eth) approximate to 0.05-a phenomenon which we attribute to the formation of the microheterogeneous structures in the binary mixture at low ethanol concentrations. Together with recent single molecule pulling experiments, these results provide new insight into the behavior of polymer chain and foreign solutes, such as enzymes, in aqueous binary mixtures.

Stiffness- and wettability-dependent myoblast cell compatibility of transparent poly(vinyl alcohol) hydrogels

This study reports the in vitro compatibility of muscle cells (C2C12 mouse myoblast cell line) with the transparent poly(vinyl alcohol) (PVA) hydrogels and the results are explained on the basis of surface wettability, crystallinity, and nanoscale elastic stiffness property. Nanoindentation was carried out with a maximum load of 100 mu N for all the hydrogel compositions and the properties such as elastic stiffness, hardness and total work done during indentation were computed. The difference in cell viability as well as adhesion of cultured myoblast cells on the investigated hydrogel substrates were discussed in reference to the difference in the nanoscale elastic properties, crystallinity, and surface wettability. An important result has been that both elastic stiffness and surface wettability synergistically influence myoblast viability/adhesion on PVA hydrogels. (c) 2012 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 2013.

Influence of nature of support on the catalytic activity of supported molybdenum-oxo species in benzyl alcohol conversion

Supported catalysts containing 15 wt.% of molybdenum have been prepared by the incipient wetness impregnation method. CaO, MgO, Al2O3, Zr(OH)4 and Al(OH)3 have been used as supports for the preparation of supported Mo catalysts. Characterisation of all the materials prepared has been carried out through BET surface area measurement, X-ray diffractometry and FT-IR spectroscopy. Catalytic activity measurements have been carried out with reference to structure-sensitive benzyl alcohol conversion in the liquid phase. The percentage conversion of benzyl alcohol to benzaldehyde and toluene varied over a large range depending on the support used for the preparation of catalysts, indicating the importance of the support on catalytic activity of Mo catalysts. Al(OH)3 has been found to be the best support for molybdenum among all the supports used. Support–metal interaction (SMI) has been found to play an important role in determining the catalytic activity of supported catalysts.

Synthesis, characterization and thermal degradation of dual temperature- and pH-sensitive RAFT-made copolymers of N,N-(dimethylamino)ethyl methacrylate and methyl methacrylate

Poly{(N,N-(dimethylamino)ethyl methacrylate]-co-(methyl methacrylate)} copolymers of various compositions were synthesized by reversible addition-fragmentation chain transfer (RAFT) polymerization at 70 degrees C in N,N-dimethylformamide. The polymer molecular weights and molecular weight distributions were obtained from size exclusion chromatography, and they indicated the controlled nature of the RAFT polymerizations; the polydispersity indices are in the range 1.11.3. The reactivity ratios of N,N-(dimethylamino)ethyl methacrylate (DMAEMA) and methyl methacrylate (MMA) (rDMAEMA = 0.925 and rMMA = 0.854) were computed by the extended KelenTudos method at high conversions, using compositions obtained from 1H NMR. The pH- and temperature-sensitive behaviour were studied in aqueous solution to confirm dual responsiveness of these copolymers. The thermal properties of the copolymers with various compositions were investigated by differential scanning calorimetry and thermogravimetric analysis. The kinetics of thermal degradation were determined by Friedmann and Chang techniques to evaluate various parameters such as the activation energy, the order and the frequency factor. (c) 2012 Society of Chemical Industry

Microwave Spectroscopic and Atoms in Molecules Theoretical Investigations on the ArPropargyl Alcohol Complex: ArHO, Ar, and ArC Interactions

The structure of the Arpropargyl alcohol (ArPA) complex is determined from the rotational spectra of the parent complex and its two deuterated isotopologues, namely ArPA-D(OD) and ArPA-D(CD). The spectra confirm a geometry in which PA exists in the gauche form with Ar located in between OH and CCH groups. All a, b and c types of transitions show small splitting due to some large-amplitude motion dominated by COH torsion, as in the monomer. Splittings in a- and b-type transitions are of the order of a few kilohertz, whereas splitting in the c-type transitions is relatively larger (0.92.6 MHz) and decreases in the order ArPA>ArPA-D(CD)>ArPA-D(OD). The assignments are well supported by ab initio calculations. Atoms in molecules (AIM) and electrostatic potential calculations are used to explore the nature of the interactions in this complex. AIM calculations not only reveal the expected OHAr and Ar interactions in the Argauche-PA complex, but also novel CAr (of CH2OH group) and OHAr interactions in the Artrans-PA complex. Similar interactions are also present in the Armethanol complex.