Studies on the vinyl polymerization photoinitiated by p-benzoylperoxybenzoic acid tert-butylester

p-Benzoylperoxybenzoic acid tert-butylester (BPE) undergoes an efficient photodecomposition producing cleavage of the peroxy bond. The excited triplet benzophenone carbonyl group of the perester is quenched by vinyl monomers (the degree of which depends on the type of monomer used) thus reducing the rate of decomposition of BPE when it is used as a photoinitiator. Radicals generated from the decomposition of BPE are highly efficient in initiating vinyl polymerization. The benzophenone-containing end groups of the polymer chain can be estimated and the carbonyl function is useful for polymer modification.     

Polymer nanoparticles: their effect on rheological,thermal, and mechanical properties of linear low‐density polyethylene (LLDPE)

Rheological, thermal, and mechanical properties of polymer particle/LLDPE blends were studied in this paper. The blends were prepared individually by incorporating nanoparticles of polystyrene (nPS) of ～60 nm and polymethyl methacrylate (nPMMA) of ～50 nm with different wt% loading (i.e., 0.10–0.5%). It was shown from the experimental results that rheological, thermal and mechanical properties were increased as polymer particles blended with LLDPE. Blends with 0.25 wt% loading of nPS and 0.5 wt% loading of nPMMA exhibited better rheological, thermal, and mechanical properties compared with that of other wt% loadings. The improvements in properties were due to the close packing of LLDPE chains as recorded by improvement in crystallinity of LLDPE with addition of nPS and nPMMA as shown by SEM. Copyright © 2010 John Wiley & Sons, Ltd.     

Characterization of mesophases of a spontaneously gel-forming compound

The phases formed by 10, 20, 30, 40 and 50 mg ml^-1 solutions of a compound, named RWJ-47428, in water have been studied with optical polarizing microscopy and X-ray diffraction. All solutions were found to exhibit the nematic liquid crystalline phase over a wide temperature range. Changes in optical textures showed a transition to the isotropic phase above 130°C in the most concentrated solution. The dimensions (length and width) of the orienting unit were determined to be 22 Å and 4.9 Å. Higher concentration samples exhibit both the nematic and the lamellar phases.     

CFD analysis for thermo-hydraulic properties in a tubular heat exchanger using curved circular rings

Journal of Thermal Analysis and Calorimetry - The never-ending demands of humans have led researchers to find more efficient energy conversion technologies. Enhancing heat transfer rate in a...     

Zur Theorie der Zustandsgleichung

Zusammenfassung Durch Festlegung zweier Diskontinuit?ten in den Daten für ges?ttigten Wasserdampf, wie sie von Zeuner in Landolt-B?rnstein's Tabellen angegeben sind, wurde eine interessante A Best?tigung der Theorie erhalten. Diese Diskontinuit?ten stellen eine Art ‚'verz?gernden Effekt“ in der Bestimmung der Konstanten dar. übersetzt von R. Riedel (Leipzig).     

Effect of salt on the phase diagrams of two binary lyotropic liquid crystalline solutions

The effect of adding salts NH₄OH and CsOH to aqueous solutions of NH₄PFO and CsPFO, respectively, was studied for concentrations in the range 0 to 2 wt %. In both systems, the isotropic to nematic and nematic to lamellar phase transition temperatures were elevated. There was an insignificant effect on the width of the nematic range in the NH₄PFO system, while the nematic phase was widened by as much as ∼3°C in the case of CsPFO. High-resolution X-ray scattering measurements were performed to determine the micellar size and its dependence on temperature for 52 wt % NH₄PFO solution in water.     

The elusive thermotropic biaxial nematic phase in rigid bent-core molecules

The biaxial nematic liquid crystalline phase was predicted several decades ago. Several vigorous attempts to find it in various systems resulted in mis-identifications. The results of X-ray diffraction and optical texture studies of the phases exhibited by rigid bent-core molecules derived from 2,5-bis-(p-hydroxyphenyl)-l,3,4-oxadiazole reveal that the biaxial nematic phase is formed by three compounds of this type. X-ray diffraction studies reveal that the nematic phase of these compounds has the achiral symmetry D_2h, in which the overall long axes of the molecules are oriented parallel to each other to define the major axis of the biaxial phase. The apex of the bent-cores defines the minor axis of this phase along which the planes containing the bent-cores of neighboring molecules are oriented parallel to each other.     

Enantioselective total synthesis of cis-(+)- and trans-(+)-disparlure

An expedient enantioselective synthetic approach for the gypsy moth sex-attractant pheromone cis-(+)-1 and trans-(+)-disparlure 2 is described employing the optimized combination of organocatalytic MacMillan’s self aldol reaction, Wittig olefination, regioselective ring opening of an epoxide and Mitsunobu esterification reactions as key steps.     

Synthesis and structural characterization of perovskite 0.65Pb(Mg1/3Nb2/3)O3-0.35PbTiO3 nanotubes

We report the synthesis and structural characterization of 0.65Pb(Mg_1/3Nb_2/3)O₃-0.35PbTiO₃ (PMN-PT) nanotubes prepared by a novel sol-gel template method. X-ray diffraction (XRD) and selected-area electron diffraction (SAED) investigations demonstrated that the postannealed (650 °C for 1 h) PMN-PT nanotubes were polycrystalline with perovskite crystal structure. The field emission scanning electron microscope (FE-SEM) shows that as prepared PMN-PT nanotubes were hollow with diameter to be about 200 nm. High resolution transmission electron microscope (HRTEM) analysis confirmed that the obtained PMN-PT nanotubes made up of nanoparticles (10-20 nm) which were randomly aligned in the nanotubes. Energy-dispersive X-ray spectroscopy (EDX) analysis confirmed the stoichiometric 0.65Pb(Mg_1/3Nb_2/3)O₃-0.35PbTiO₃. The possible formation mechanism of PMN-PT nanotubes was proposed at the end.