Nafion®/(organically modified silicate) nanocomposites via polymer in situ sol–gel reactions: Mechanical tensile properties

A series of Nafion®/[organically modified silicate (ORMOSIL)] hybrid materials have been created by in situ sol–gel copolymerizations of tetraethylorthosilicate and semiorganic silicon alkoxide monomers. The trends in the mechanical tensile properties of these hybrid materials were largely rationalized in terms of the entrapment of the long sulfonic acid side chains in silicate or ORMOSIL structures. There is a significant increase in the mechanical strength relative to that of unfilled Nafion®, except in one case. Young's modulus is enhanced relative to that of unfilled acid form Nafion® in a number of cases, although the degree of ductility is reduced relative to that of unfilled Nafion®. The filler fractions are beneath a critical value that would reflect percolation of a glassy, direct load‐bearing silicate phase. © 2002 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 40: 2237–2247, 2002     

Synthesis of novel conjugated polymer based on cyclopenta[def]phenanthrene and vinylene with strong interchain interaction

In this study, a novel conjugated polymer, poly(4,4‐bis(2‐ethylhexyl)‐4H‐cyclopenta[def]phenanthrene‐2,6‐vinylene) (PCPPV) has been synthesized and characterized. For the polymerization, Gilch's reaction was applied for the first time with the cyclopenta[def]phenanthrene system. The absorption and emission spectra of PCPPV are red‐shifted about 40–50 nm due to the vinylene units when compared with those of poly(2,6‐(4,4‐bis(2‐ethylhex‐yl)‐4H‐cyclopenta[def]phenanthrene)) (PCPP). The solid‐state fluorescence is significantly broadened, possibly due to π–π interactions introduced by the phenanthrene and vinylene moieties. In solution, as the concentration of polar solvent increased, the photoluminescence (PL) intensity decreased due to quenching and aggregation by the interchain interactions between the conjugated backbones. After annealing the film at 80 °C, the PL and electroluminescence (EL) emission spectra exhibited also the quenching and aggregation effects indicating the interchain interactions of PCPPV. The large number of aromatic rings in a unit and the increased planarity achieved through introduction of vinylene units are able to give interchain interactions stronger than fluorene or phenylene units. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 5068–5077, 2009     

Exergy efficiency of a counterflow air/air heat exchanger with vapour condensation

The exergy efficiency of a counterflow hot moist air/ambient air heat exchanger with vapour condensation as a function of the temperature and humidity of the hot moist air, the ratio of ambient air flow rate to hot moist air flow rate and the minimum temperature differences between the flows is determined. The ranges 20 to 120°C and 0.01 to 1.0 kg·kg^–1 for the temperature and humidity ratio of hot moist air respectively are considered. Constant ambient air conditions of 20°C and 0.01 kg·kg^–1 were assumed.

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Exergie-Wirkungsgrad eines Luft/Luft-Gegenstrom-Wärmetauschers mit Dampfkondensation

Zusammenfassung Der Exergie-Wirkungsgrad eines Gegenstrom-Wärmetauschers wird bestimmt für die Kombination: heiße Feuchtluft zu Umgebungsluft mit Dampfkondensation, und zwar als Funktion von Temperatur und Feuchtegrad der heißen Feuchtluft, des Verhältnisses von Umgebungsluft zu heißen Feuchtluftstrom und der minimalen Temperaturdifferenz zwischen beiden Strömen. Die Temperatur des heißen Feuchtluftstroms variiert im Bereich von 20 bis 120°C, sein Feuchtegrad im Bereich 0,01 bis 1,0. Bezüglich der Umgebungsluft wurden konstante Bedingungen angenommen, und zwar 20°C und ein Feuchtegrad von 0,01.

     

Effect of acidification treatment and morphological stability of sulfonated poly(arylene ether sulfone) copolymer proton‐exchange membranes for fuel‐cell use above 100 °C

Directly copolymerized wholly aromatic sulfonated poly(arylene ether sulfone) copolymers derived from 4,4′‐biphenol, 4,4′‐dichlorodiphenyl sulfone, 3,3′‐disulfonated, and 4,4′‐dichlorodiphenyl sulfone (BPSH) were evaluated as proton‐exchange membranes for elevated temperature operation (100–140 °C). Acidification of the copolymer from the sulfonated form after the nucleophilic step (condensation) copolymerization involved either immersing the solvent‐cast membrane in sulfuric acid at 30 °C for 24 h and washing with water at 30 °C for 24 h (method 1) or immersion in sulfuric acid at 100 °C for 2 h followed by similar water treatment at 100 °C for 2 h (method 2). The fully hydrated BPSH membranes treated by method 2 exhibited higher proton conductivity, greater water absorption, and less temperature dependence on proton conductivity as compared with the membranes acidified at 30 °C. In contrast, the conductivity and water absorption of a control perfluorosulfonic acid copolymer (Nafion 1135) were invariant with treatment temperature; however, the conductivity of the Nafion membranes at elevated temperature was strongly dependent on heating rate or temperature. Tapping‐mode atomic force microscope results demonstrated that all of the membranes exposed to high‐temperature conditions underwent an irreversible change of the ionic domain microstructure, the extent of which depended on the concentration of sulfonic acid sites in the BPSH system. The effect of aging membranes based on BPSH and Nafion at elevated temperature on proton conductivity is also discussed. © 2003 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 41: 2816–2828, 2003     

Bose-einstein correlations in the target fragmentation region in 200A GeV16O+nucleus collisions

Correlations between positive pions are investigated in the target fragmentation region of 200A GeV¹⁶O+nucleus collisions. The pions are measured with the Plastic Ball detector in the WA80 experiment at the CERN SPS. The target mass dependence of the radii and the correlation strength extracted by interferometry is studied. A new approach to the fit of the correlation function is introduced. The correlation strength and both invariant and transverse radii increase with decreasing target mass. The transverse radius for¹⁶O+C reactions appears to be much larger than the geometrical radius of the nuclei involved. For the Au target only a small fraction of the measured pions contributes to the apparent correlation. Hints for a much larger second component in¹⁶O+Au reactions are observed. Rescattering phenomena may provide a clue to understand these phenomena.     

Rapid fluorimetric assay for the detection of the peptidyl alpha-amidating enzyme intermediate using high-performance liquid chromatography.

Peptidylglycine alpha-amidating enzyme catalyzes the conversion of glycine-extended peptides to their corresponding amidated peptides via a stable alpha-hydroxyglycine intermediate. Using a new rapid fluorimetric reversed-phase high-performance liquid chromatographic assay, we have demonstrated that the substrate and product of the amidation reaction, as well as both stereoisomers of the alpha-hydroxyglycine intermediate, can be separated and detected in quantities as low as 1 pmol. The method is highly reproducible and requires less than 11 min for separation and quantification.     

Steady state Joule heating with temperature dependent conductivities

A general solution is given to the nonlinear steady state heat conduction equation for the case in which a metal is heated by electrical conduction currents. The solution is valid for any temperature variation in the thermal and electrical conductivities and is illustrated by application to a typical Joule heating situation in one dimension. Comparison of the case of temperature dependent conductivities for a metal with the solution which assumes both of these conductivities to remain constant with varying temperature reveals some interesting differences between the two cases.