Growth regimes and spherulites in thin-film poly(ɛ-caprolactone) with amorphous polymers

Spherulite ring-band patterns and growth regimes in neat poly(?-caprolactone) (PCL) and its miscible blends were analyzed using polarized-light optical microscopy and differential scanning calorimetry (DSC). Spherulite growth in thin-film forms and transformation of spherulite patterns in different regimes were investigated by comparing neat PCL with its miscible blends. Three miscible diluents in PCL were probed: poly(p-vinyl phenol) (PVPh), poly(benzyl methacrylate) (PBzMA), and poly(phenyl methacrylate) (PPhMA), which represent strong H-bonding and weak polar interactions, respectively. Blending of PCL with miscible amorphous polymers changes the spherulite patterns significantly. The effect of different diluent polymers varies. Inclusion of different amorphous polymers in PCL leads to different extents of suppression in growth rates and induces different spherulitic patterns. The H-bonding interaction leads to that the PCL/PVPh blend shows dendritic crystals and no ring bands. Although PPhMA differs from PBZMA only by a methylene in the chemical structure of repeat unit, the coil-like textures of ring bands in the PCL/PPhMA blend are widely different from the zig-zag ring bands in the PCL/PBzMA blend. Regime plots show that the growth of neat PCL behaves quite differently from any of its blends with amorphous polymers (PVPh, PPhMA, or PBzMA). Regime plots for PCL/PBzMA blend also differ from those for the PCL/PPhMA blend, which correlates with the crystal patterns seen in these two blend systems.     

Preparation and decarboxylative rearrangement of (Z)-enyne esters

A method to assemble (Z)-enyne esters via palladium-catalyzed cross coupling reactions of enol tosylates is reported. A base-mediated one-pot decarboxylative rearrangement of the enynes to enones is described. The scope of this process is examined.     

Effect of ultra-fine gold particle addition to metal oxides in ethylene oxidation

Oxidation of ethylene was carried out over alumina-supported metal oxide catalysts and highly dispersed gold catalysts, respectively, under atmospheric pressure. The ethylene was completely oxidized to produce carbon dioxide and water with both metal oxide and gold catalysts. The activity of gold catalyst prepared by deposition method was much higher than that of supported metal oxide catalysts. Ultra-fine gold particles on Co₃O₄ were more active than on Al₂O₃. Fe₂O₃/Al₂O₃ and MnO₂/Al₂O₃ catalysts were more active than MoO₃/Al₂O₃ catalyst. The activity of the supported metal oxide catalysts was greatly enhanced by addition of gold particles. It was therefore considered that gold particles promote dissociative adsorption of oxygen and the adsorbed oxygen reacts with adsorbed ethylene on support adjacent to the active site.     

The effect of alkaline earth metal oxide on nickel catalyst for carbon dioxide reforming of methane

A study on the effect of alkaline earth metal oxide on the activity and stability of nickel catalyst for carbon dioxide reforming of methane was performed. When CaO, SrO, and BaO were used as supports, there was no difference in catalytic activity between the catalysts made by coprecipitation and impregnation. However, when MgO was used as a support, the catalyst prepared by coprecipitation showed superior activity than that made by impregnation. The higher activity of the catalyst made by coprecipitation was due to the formation of solid solution consisting of nickel and magnesium. The formation of the solid solution enhanced the dispersion of nickel and the resistance to coke formation.     

Diffusion of chromium in chrysoberyl

Cr³⁺ diffusion in chrysoberyl (BeAl₂O₄) irradiated by H⁺ ions and electrons has been studied and compared with diffusion in non-irradiated samples. Chrysoberyl crystals were irradiated with 6 MeV H⁺ ions to fluencies of 1×10¹⁶ cm^–2 for 25 min and with 10 MeV electrons to fluencies of 2×10¹⁷ cm^–2 for 1 h. Three different types of samples, which were doped with Cr³⁺, were annealed in horizontal alumina tube furnaces by 50 K intervals in the temperature range from 1773 to 1923 K for 200 h. Scanning electron microscope–energy dispersive X-ray spectrometer (SEM–EDX) was used to measure the diffusion. Arrhenius equations for the diffusion coefficient for Cr³⁺ in the temperature range 1773–1923 K were developed:     

Interactive group decision-making procedure using weak strength of preference

In the paper, we present an interactive decision procedure for aggregating group members’ preferences which are specified in incomplete ways. A group consensus under incomplete information is not usually reached at a single step since less-specific preferences on attribute weights and performance scores make a clear selection of best alternative more difficult. To circumvent these difficulties, a measure, indicating the strength of preference between alternatives, is derived to help each of decision makers change his/her preference structure. To make preference changes based on the measure effective, we present a solution method to convert an intractable nonlinear programme into a linear one.     

The emission wavelength tuning of InAs/InP quantum dots with thin GaAs, InGaAs, InP capping layers by MOCVD

InAs quantum dots (QDs) were grown on InP substrates by metalorganic chemical vapor deposition. The width and height of the dots were 50 and 5.8 nm, respectively on the average and an areal density of 3.0×10¹⁰ cm⁻² was observed by atomic force microscopy before the capping process. The influences of GaAs, In_0.53Ga_0.47As, and InP capping layers (5–10 ML thickness) on the InAs/InP QDs were studied. Insertion of a thin GaAs capping layer on the QDs led to a blue shift of up to 146 meV of the photoluminescence (PL) peak and an InGaAs capping layer on the QDs led to a red shift of 64 meV relative to the case when a conventional InP capping layer was used. We were able to tune the emission wavelength of the InAs QDs from 1.43 to 1.89 μm by using the GaAs and InGaAs capping layers. In addition, the full-width at half-maximum of the PL peak decreased from 79 to 26 meV by inserting a 7.5 ML GaAs layer. It is believed that this technique is useful in tailoring the optical properties of the InAs QDs at mid-infrared regime.     

A nanoscale field effect data storage of bipolar endo-fullerenes shuttle device

We investigated the internal dynamics of an electro-fluid shuttle memory element, consisting of K⁺@C₆₀ and F⁻@C₆₀ encapsulated in a C₆₄₀ nanocapsule. Energetics and operating responses of bipolar endo-fullerenes shuttle memory device, (K⁺@C₆₀–F⁻@C₆₀)@C₆₄₀, were examined by classical molecular dynamics simulations under the external force fields.     

Fluorene‐based alternating polymers containing electron‐withdrawing bithiazole units: Preparation and device applications

We report here the synthesis via Suzuki polymerization of two novel alternating polymers containing 9,9‐dioctylfluorene and electron‐withdrawing 4,4′‐dihexyl‐2,2′‐bithiazole moieties, poly[(4,4′‐dihexyl‐2,2′‐bithiazole‐5,5′‐diyl)‐alt‐(9,9‐dioctylfluorene‐2,7‐diyl)] (PHBTzF) and poly[(5,5′‐bis(2″‐thienyl)‐4,4′‐dihexyl‐2,2′‐bithiazole‐5″,5″‐diyl)‐alt‐(9,9‐dioctylfluorene‐2,7‐diyl)] (PTHBTzTF), and their application to electronic devices. The ultraviolet–visible absorption maxima of films of PHBTzF and PTHBTzTF were 413 and 471 nm, respectively, and the photoluminescence maxima were 513 and 590 nm, respectively. Cyclic voltammetry experiment showed an improvement in the n‐doping stability of the polymers and a reduction of their lowest unoccupied molecular orbital energy levels as a result of bithiazole in the polymers' main chain. The highest occupied molecular orbital energy levels of the polymers were ?5.85 eV for PHBTzF and ?5.53 eV for PTHBTzTF. Conventional polymeric light‐emitting‐diode devices were fabricated in the ITO/PEDOT:PSS/polymer/Ca/Al configuration [where ITO is indium tin oxide and PEDOT:PSS is poly(3,4‐ethylenedioxythiophene) doped with poly(styrenesulfonic acid)] with the two polymers as emitting layers. The PHBTzF device exhibited a maximum luminance of 210 cd/m² and a turn‐on voltage of 9.4 V, whereas the PTHBTzTF device exhibited a maximum luminance of 1840 cd/m² and a turn‐on voltage of 5.4 V. In addition, a preliminary organic solar‐cell device with the ITO/PEDOT:PSS/(PTHBTzTF + C₆₀)/Ca/Al configuration (where C₆₀ is fullerene) was also fabricated. Under 100 mW/cm² of air mass 1.5 white‐light illumination, the device produced an open‐circuit voltage of 0.76 V and a short‐circuit current of 1.70 mA/cm². The fill factor of the device was 0.40, and the power conversion efficiency was 0.52%. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 1845–1857, 2005