bluuebunny/crossref_metadata_2025 huggingface dataset:
Optimization of anti‐reflection moth‐eye structures for use in crystalline silicon solar cells
Authors: Yamada Noboru , Kim Oanh Ngo , Tokimitsu Toru , Nakai Yusuke , Masuda Hideki
Published: May 2010

An anti‐reflection (AR) moth‐eye structure made of acrylic resin and deposited on a polyethylene terephthalate (PET) substrate was optimized in the wavelength range from 400 to 1170 nm; crystalline silicon (c‐Si) solar cells function efficiently in this wavelength range. The rigorous coupled wave analysis (RCWA) method was used for optical simulation, and the Taguchi method was used for efficient optimization. The simulation results showed that the reflectance of the optimized structure over the above‐mentioned wavelength range was less than 0.87% and that a minimal reflectance of 0.1% was observed at 400 nm. Experimental results showed that the reflectance of a fabricated moth‐eye structure was less than 1.0% in the wavelength range and that a minimal reflectance of 0.55% was observed at 700 nm. A c‐Si solar cell, which was enclosed in a polyvinyl butyral (PVB) layer of uniform thickness, was coated with the fabricated moth‐eye film, and it was observed that the moth‐eye film increased electric generation (EG) up to 15%, depending on the incident angle. Further, a daily increase in EG of up to 8.7% was estimated on a clear summer day in Japan when the moth‐eye film was used. Copyright © 2010 John Wiley & Sons, Ltd.
Kinetic investigation of the RAFT polymerization of p‐acetoxystyrene
Authors: Cauët Solène I. , Wooley Karen L.
Published: May 2010

The kinetics of the RAFT polymerization of p‐acetoxystyrene using a trithiocarbonate chain transfer agent, S‐1‐dodecyl‐S′‐(α,α′‐dimethyl‐α″‐acetic acid)trithiocarbonate, DDMAT, was investigated. Parameters including temperature, percentage initiator, concentration, monomer‐to‐chain transfer agent ratio, and solvent were varied and their impact on the rate of polymerization and quality of the final polymer examined. Linear kinetic plots, linear increase of Mn with monomer conversion, and low final molecular weight dispersities were used as criteria for the selection of optimized polymerization conditions, which included a temperature of 70 or 80 °C with 10 mol % AIBN initiator in bulk for low conversions or in 1,4‐dioxane at a monomer‐to‐solvent volume ratio of 1:1 for higher conversions This study opens the way for the use of DDMAT as a chain transfer agent for RAFT polymerization to incorporate p‐acetoxystyrene together with other functional monomers into well‐defined copolymers, block copolymers, and nanostructures. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 2517–2524, 2010
Ring‐opening metathesis copolymerization of cyclooctene and a carborane‐containing oxanorbornene
Authors: Simon Yoan C. , Coughlin E. Bryan
Published: May 2010

The incorporation of a silyl‐protected oxanorbornene imide carborane (SONIC) in polyethylene‐like materials is reported. These copolymers were obtained via ring‐opening metathesis copolymerization of (SONIC) and cyclooctene followed by hydrogenation with p‐toluenesulfonylhydrazide. The composition of the copolymer was varied by altering the feed ratio. Structural and thermal properties were investigated and compared with that of a model polymer so as to gauge the impact on the inclusion of the silyl‐functionalized carborane. An initial observation of the modification of the chain sequence upon changing solvent polarity is also discussed. Finally, the potential utilization of these materials as radiation shielding materials is mentioned. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 2557–2563, 2010
Conjugated polymers with broad absorption: Synthesis and application in polymer solar cells
Authors: Song Jinsheng , Zhang Chi , Li Cuihong , Li Weiwei , Qin Ruiping , Li Binsong , Liu Zhengping , Bo Zhishan
Published: May 2010

A series of main chain donor‐acceptor low‐bandgap conjugated polymers were designed, synthesized, and used for the fabrication of polymer solar cells. The absorption spectra of low‐bandgap conjugated polymers were tuned by the ratio of three copolymerization monomers. The polymers in films exhibited broad absorption ranging from 300 to 1000 nm with optical bandgaps of around 1.40 eV. All of the polymers have been investigated as an electron donor in photovoltaic cells blending with PCBM ([6, 6]‐phenyl C61‐butyric acid methyl ester) as an electron acceptor and power conversion efficiencies (PCEs) of 1.32–1.8% have been obtained. As for P1, PCE increases from 1.67 to 2.44% after adding 1,8‐diiodooctance as an additive. The higher PCEs are probably because of better phase separation of blend films. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 2571–2578, 2010
Modeling multiphase latex particle equilibrium morphology
Authors: Reyes Yuri , Asua José M.
Published: May 2010

Multiphase waterborne polymer particles provide advantages in more demanding applications and their performance depends on particle morphology. Currently, no general approach to predict the morphology of multiphase latex particles is available. In this work, a model based on Monte Carlo methods was developed for the prediction of equilibrium morphologies of multiphase waterborne systems, such as polymer‐polymer and polymer‐polymer‐inorganic hybrids. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 2579–2583, 2010
Highly refractive polymer resin derived from sulfur‐containing aromatic acrylate
Authors: You Nam‐Ho , Higashihara Tomoya , Ando Shinji , Ueda Mitsuru
Published: May 2010

New sulfur‐containing polymers with high‐refractive indices and low birefringences have been developed as UV‐curable high‐refractive polymer resins. The polymers derived from 2,7‐bis[(2‐acryloylethyl)sulfanyl]thianthrene (2,7‐BAST) and 4,4′‐bis[(acryloyloxyethylthio)diphenylsulfide (4,4′‐BADS) were prepared by photopolymerization under UV irradiation. Transparent UV‐cured films were obtained in both cases. Both polymers showed good thermal stability, such as a 5% weight‐loss temperature at 355 °C under nitrogen and glass transition temperatures (Tg) in the range of 94–143 °C. They also showed high‐refractive indices of 1.6531 and 1.6645 at 632.8 nm and low birefringences of 0.0039 and 0.0069 in addition to high transparency in the visible region. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 2604–2609, 2010
Free radical and nitroxide mediated polymerization of hydroxy–functional acrylates prepared via lipase–catalyzed transacylation reactions
Authors: Popescu Dragos , Hoogenboom Richard , Keul Helmut , Möller Martin
Published: May 2010

3‐Hydroxypropyl acrylate, 4‐hydroxybutyl acrylate, 2‐methyl‐3‐hydroxypropyl acrylate, 2‐hydroxypropyl acrylate, neopentyl glycol acrylate, glyceryl acrylate, and dihydroxyhexyl acrylate were prepared via transacylation reaction of methyl acrylate with diols and triols catalyzed by Candida antarctica lipase B. After removal of the enzyme by filtration and the methyl acrylate by distillation, the monomers were polymerized via free radical polymerization (FRP) with azobisisobutyronitrile as initiator and nitroxide mediated polymerization (NMP) employing Blocbuilder™ alkoxyamine initiator and SG‐1 free nitroxide resulting in hydroxy functional poly(acrylates). The NMP kinetics are discussed in detail. In addition, the polymers obtained by FRP and NMP are compared and the results are related to the amount of bisacrylates that are present in the initial monomer mixtures resulting from the transacylation reactions. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 2610–2621, 2010
Modifications of the active sites distribution in the Ziegler‐Natta polymerization of propylene using Lewis acids
Authors: Ribour David , Spitz Roger , Monteil Vincent
Published: May 2010

Heterogeneous Ziegler‐Natta precatalysts (with phthalate as internal donor) were modified by treatments with various Lewis acids (MCln with M = Ga, Sn, Si, and Sb and n = 3, 4, or 5) before their use in the polymerization of propylene. If performed on previously “detitanated” precatalysts, treatments with SnCl4 and SiCl4 lead to a slight activation but especially to an increase of the tacticity whereas GaCl3 and SbCl5 treatments deactivate the catalyst. The modification method applied to conventional unmodified precatalysts gave similar trends. A significant increase of tacticity (and/or of Tm) and a narrowing of the molecular weight distribution were observed in the case of SnCl4 and SiCl4 treatments. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 2631–2635, 2010
Facile one‐pot synthesis of linear and radial block copolymers of styrene and isoprene through a novel coupling agent by living anionic polymerization
Authors: Kumar Santosh , Shah Priyank N. , Kang Beom‐Goo , Min Joon‐Keun , Hwang Woon Sung , Sung Ik Kyung , Shah Shailesh R. , Murthy Chivukula N. , Ahn Seonyoung , Chang Taihyun , Lee Jae‐Suk
Published: May 2010

A new methodology is successfully used for the concurrent synthesis of three different copolymers; diblock, triblock, and three‐armed star‐block copolymers of styrene and isoprene via the living anionic polymerization with control over the molecular weight and weight fractions of each block. The room temperature polymerization process has resulted in the well defined linear and radial block copolymers, when the living di‐block of poly(styrene‐b‐isoprene) was coupled using cheap and readily available malonyl chloride as a novel coupling agent giving nearly 100% yield. The resulting block copolymers have narrow polydispersity index (PDI = 1.01–1.09) with a good agreement between the calculated and the observed molecular weights. The results are further supported by fractionation of the block copolymers by reversed‐phase temperature gradient interaction chromatography (RP‐TGIC) technique followed by size exclusion chromatography (SEC). © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 2636–2641, 2010
Poly(N‐vinylcarbazole) chemically modified graphene oxide
Authors: Zhang Bin , Chen Yu , Zhuang Xiaodong , Liu Gang , Yu Bo , Kang En‐Tang , Zhu Jinhui , Li Yongxi
Published: May 2010

A new soluble donor‐acceptor type poly(N‐vinylcarbazole)‐covalently functionalized graphene oxide (GO‐PVK) has been synthesized by reaction of DDAT (S‐1‐dodecyl‐S′‐(α,α′‐dimethyl‐α″‐aceticacid)trithiocarbonate)‐PVK with GO‐toluene‐2,4‐diisocynate. The incorporation of sufficient amount of PVK chains makes the modified GO nanosheets readily dispersible in organic solvents. The resulting material exhibits an enhanced solubility of 10 mg/mL in organic solvents. Covalent grafting of PVK onto the edge and surface of GO nanosheets did not change the carbazole absorption in the ultraviolet region, but substantially reduced the absorption intensity of GO in the visible region. The intensity of the emission band of GO‐PVK at 437 nm was a little bit quenched when compared with that of DDAT‐PVK, suggesting intramolecular quenching from PVK to GO. Such intramolecular quenching process may involve energy or electron transfer between the excited singlet states of the PVK moiety and the GO moiety. The HOMO/LUMO values and the energy bandgap of GO‐PVK experimentally estimated by the onset of the redox potentials are −5.60, −3.58, and 2.02 eV, respectively. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 2642–2649, 2010
Cationic polymerization of L,L‐lactide
Authors: Baśko Małgorzata , Kubisa Przemysław
Published: May 2010

Cationic bulk polymerization of L,L‐lactide (LA) initiated by trifluromethanesulfonic acid [triflic acid (TfA)] has been studied. At temperatures 120–160 °C, polymerization proceeded to high conversion (>90% within ∼8 h) giving polymers with Mn ∼ 2 × 104 and relatively high dispersity. Thermogravimetric analysis of resulting polylactide (PLA) indicated that its thermal stability was considerably higher than the thermal stability of linear PLA of comparable molecular weight obtained with ROH/Sn(Oct)2 initiating system. Also hydrolytic stability of cationically prepared PLA was significantly higher than hydrolytic stability of linear PLA. Because thermal or hydrolytic degradation of PLA starting from end‐groups is considerably faster than random chain scission, both thermal and hydrolytic stability depend on molecular weight of the polymer. High thermal and hydrolytic stability, in spite of moderate molecular weight of cationically prepared PLA, indicate that the fraction of end‐groups is considerably lower than in linear PLA of comparable molecular weight. According to proposed mechanism of cationic LA polymerization growing macromolecules are fitted with terminal OH and C(O)OSO2CF3 end‐groups. The presence of those groups allows efficient end‐to‐end cyclization. Cyclic nature of resulting PLA explains its higher thermal and hydrolytic stability as compared with linear PLA. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 2650–2658, 2010
Reactivities of carbocations and monomers in carbocationic polymerization and copolymerization
Authors: Sigwalt Pierre , Moreau Michel
Published: May 2010

In carbocationic polymerization and copolymerization, a recent publication concluded that the substituent effect on carbocation reactivity is much larger than its effect on monomer reactivity, and this by a factor 106 in the case of the rate constant k12capp for p‐methylstyrene addition (monomer M2) on, respectively, poly(p‐methoxystyrene)± or poly(p‐methylstyrene)± (M). This conclusion is disputed, as well as the assumption that the rate constants of capping (k12capp) obtained in deactivation reactions of poly(p‐methoxystyrene)± are identical with cross propagation rate constants in copolymerization (k12copol). It is shown that the large calculated k12capp are based on propagation constant values for p‐methylstyrene (k ≈ 109) obtained by the diffusion‐clock method. They are 104 times smaller as found for all styrenes, that is, between 104 and 105 when they are based on the ionic species concentrations. In such a case, the available data are still in agreement with an approximate compensation between the reactivities of a monomer and of the corresponding carbocation. It is also shown that copolymerization data for styrenes are not compatible with k values near to diffusion control, and that variations of log k12capp and log k12copol with the nucleophilicity parameter N of the monomers indicate a much lower selectivity of the monomers in the case of copolymerization. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 2666–2680, 2010
Evaluation of peroxide initiators for radical polymerization‐based self‐healing applications
Authors: Wilson Gerald O. , Henderson James W. , Caruso Mary M. , Blaiszik Benjamin J. , McIntire Patrick J. , Sottos Nancy R. , White Scott R. , Moore Jeffrey S.
Published: May 2010

The suitability of various peroxide initiators for a radical polymerization‐based self‐healing system is evaluated. The initiators are compared using previously established criteria in the design of ring opening metathesis polymerization‐based self‐healing systems. Benzoyl peroxide (BPO) emerges as the best performing initiator across the range of evaluation criteria. Epoxy vinyl ester resin samples prepared with microcapsules containing BPO exhibited upwards of 80% healing efficiency in preliminary tests in which a mixture of acrylic monomers and tertiary amine activator was injected into the crack plane of the sample after the initial fracture. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 2698–2708, 2010
Synthesis of phenanthroline‐terminated polymers and their Fe(II)‐complexes
Authors: Nagy Miklós , Zsuga Miklós , Rácz Dávid , Kéki Sándor
Published: May 2010

Well‐defined mono‐ and bifunctional, phenanthroline‐terminated poly(ethylene glycol) and polyisobutylene capable of polymer network formation were synthesized. The starting materials mono‐ and bi‐phenanthroline‐ (phen) terminated poly(ethylene glycols) (mPEG‐phen, phen‐PEG‐phen) and polyisobutylenes (PIB‐phen, phen‐PIB‐phen) were prepared by the Williamson synthesis and characterized by means of 1H NMR and MALDI‐TOF mass spectrometry. According to UV–Vis spectrophotometry and ESI‐TOF mass spectrometry, the phenanthroline‐terminated polymers underwent quantitative complex formation with ferrous ions in solution. The aqueous solution of mPEG‐phen shows self‐assembly behavior. Important parameters, such as critical micelle concentration and hydrodynamic radius of the aggregates were also determined. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 2709–2715, 2010
Immortal SET–LRP mediated by Cu(0) wire
Authors: Jiang Xuan , Rosen Brad M. , Percec Virgil
Published: May 2010

Cu(0)‐wire/Me6‐TREN is a well established catalyst for living radical polymerization via SET–LRP. Here, it is demonstrated that this polymerization is not just living, but it is in fact the first example of immortal living radical polymerization. The immortality of SET–LRP mediated with Cu(0) wire was demonstrated by attempting, in an unsuccessful way, to irreversible interrupt multiple times the polymerization via exposure to O2 from air. SET–LRP indeed stopped each time when the reaction mixture was exposed to air. However, the SET–LRP reaction, was restarted each time after resealing the reaction vessel and reestablishing the catalytic cycle with the same Cu(0) wire, to produce the same conversion as in the conventional uninterrupted SET–LRP process. Despite the interruption by O2, the reactivated SET–LRP had a good control of molecular weight, molecular weight evolution, and molecular weight distribution, with perfect retention of chain‐end fidelity. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 2716–2721, 2010
Nanoporous and proton conductive hydrophobic–hydrophilic copolymer thermoset membranes
Authors: Rahmathullah M. Aflal M. , Snyder Joshua D. , Elabd Yossef A. , Palmese Giuseppe R.
Published: May 2010

Copolymers of hydrophobic diglycidyl ether of bisphenol A (DGEBA) vinyl ester (VE) and hydrophilic 2‐acrylamido 2‐methyl 1‐propane sulfonic acid (AMPS) were evaluated as proton conducting membranes for fuel cell applications. Membranes were synthesized using free radical copolymerization in the presence of a common solvent for both monomers, dimethyl formamide (DMF), followed by solvent removal by supercritical CO2 to induce porosity. Micrographs revealed pore sizes below 60 nm with porosity proportional to the initial solvent fraction used. Studies on the states of water showed that the presence of this pore volume significantly altered the freezable water fraction at equivalent AMPS concentrations. Comparison of the moles of water per mole of sulfonic acid (λ) between copolymer membranes and AMPS monomer solutions showed that the nonfreezable water (λ|nonfr) was depressed at high AMPS concentrations, suggesting that differences in interatomic distances between sulfonic acid groups might alter λ|nonfr. The highest average through plane conductivity of membranes was determined to be 30 mS/cm and was comparable to that of Nafion®117 (27 mS/cm). The effective proton mobility, μeff, was calculated and suggested to be a parameter used to capture the effects of membrane structure and swelling while acting as a comparison between different membrane types. Fuel cell tests on membranes at low ion exchange capacities were compared to Nafion®117, with suggestions on improvements of copolymer structures for improved performance. © 2010 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 48: 1245–1255, 2010
Effects of TEMED and EDTA on the structural and mechanical properties of NIPAAm/Na+MMT composite hydrogels
Authors: Yumakgil Kübra , Gökçeören Argun Talat , Erbil Candan
Published: May 2010

N‐isopropyl acrylamide (NIPAAm) hydrogels are known as thermosensitive crosslinked polymer networks. In this work, the network parameters of their composites, i.e., NIPAAm/sodium montmorillonite (NIPAAm/Na+MMT) hydrogels synthesized by free radical solution polymerization in the presence of two different types of accelerator (tetramethyl ethylenediamine (TEMED) and ethylenediamine tetraacetic acid (EDTA)) and initiator (potassium persulphate (K2S2O8) and cerium ammonium nitrate ((NH4)2Ce(NO3)6), Ce(IV)) using five different clay content (in the range of 1.0–5.0 wt % of total monomer concentration) at 25 °C were presented and discussed. FTIR spectra, XRD patterns, SEM photographs, and network parameters of the samples indicated that the presence of COOH groups on EDTA molecules was resulted in the formation of exfoliated structures and the activity of EDTA/KPS redox pair was higher than those of TEMED/KPS and EDTA/Ce (IV) pairs. The compression moduli (G) of the hydrogels initiated with EDTA/Ce(IV) redox pair showed smooth and continual changings with increase in Na+MMT content (for swelling equilibrium at 25 °C) on the contrary of EDTA/KPS and TEMED/KPS pairs. It might be related to low initiator efficiency of cerium ammonium nitrate than KPS molecules, having higher effective crosslinking density with increasing clay content. On the other hand, the G moduli of NIPAAm/Na+MMT hydrogels (above their phase transition temperature) initiated with TEMED/KPS redox pair were higher than the others because of the more hydrophobic nature of TEMED molecules. © 2010 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 48: 1256–1264, 2010
Relaxation of fibrils in blends with one viscoelastic component: From bulk to confined conditions
Authors: Cardinaels R. , Moldenaers P.
Published: May 2010

Using a counter rotating parallel plate shear flow cell, shape relaxation of fibrils in a quiescent matrix is studied microscopically. Both the effects of geometrical confinement and component viscoelasticity are systematically explored. By applying a supercritical shear flow for varying amounts of time, droplets with a wide range of initial elongation ratios have been generated. The shape relaxation of these elongated droplets occurs in two stages; the first one consists of shape changes and retraction from a fibril to an ellipsoid, the second one is the retraction of this ellipsoid to a sphere. During both stages of the relaxation process, droplet viscoelasticity has no influence on the relaxation, whereas matrix viscoelasticity and geometrical confinement result in a slower retraction. However, the effect of confinement on the shape relaxation during the first stage of the relaxation process is less pronounced than its influence on the retraction of ellipsoidal droplets. The relaxation time of the second stage of the relaxation corresponds to the relaxation time of initially ellipsoidal droplets. Finally, for confinement ratios up to 0.75 and Deborah numbers around 1, no effect of confinement and component viscoelasticity on the critical initial elongation ratio for breakup during relaxation has been found. © 2010 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 48: 1372–1379, 2010
Viscoelastic properties of decrosslinked irradiation‐crosslinked polyethylenes in supercritical methanol
Authors: Kwon Yong Jin , Hong Soon Man , Koo Chong Min
Published: May 2010

The viscoelastic properties of decrosslinked irradiation‐crosslinked polyethylenes using a supercritical methanol were investigated via oscillatory dynamic shear measurements. Decrosslinked polymers at a low reaction temperature exhibited solid‐like rheological properties, as evidenced by a small slope at G′ and G″, a long relaxation time, slow stress relaxation behavior, and considerable yield stress. In contrast, decrosslinked polymers at a high temperature exhibited liquid‐like rheological properties that included a large slope in G′ and G″, a short relaxation time, fast stress relaxation behavior, and nonyield stress. The difference in the viscoelastic properties of the decrosslinked polyethylenes was attributed to the difference in the gel content with the reaction temperature. A higher gel content induced stronger solid‐like viscoelastic properties. Hence, the rheological measurements were useful for analyzing the molecular structure of decrosslinked polymers using a supercritical fluid. © 2010 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 48: 1265–1270, 2010
Cavitation and morphological changes in polypropylene deformed at elevated temperatures
Authors: Pawlak Andrzej , Galeski Andrzej
Published: May 2010

Polypropylene (PP) thick films were subjected to tensile drawing at various temperatures from the room temperature to 100 °C. Morphological alterations during drawing were followed by wide‐angle X‐ray scattering, small‐angle X‐ray scattering, and scanning electron microscopy (SEM) of sectioned and etched samples, volume strain measurement, and light transparency measurement at various level of strain. The morphological observations were paralleled with stress–strain determination. Samples drawn at 25 and 40 °C undergo severe cavitation contributing to their volume increase up to 90–95%. The volume increase contributes greatly to the engineering strain. PP drawn at 70 and 100 °C does not cavitate. At the strain up to 1.2, a high lamellae orientation is observed in SEM, whereas the 2D WAXS patterns show in contrary circular diffraction rings indicating low orientation of crystals. The rotation of lamellae toward drawing direction is associated with reverse rotation of chains in crystals due to fine chain slips. These two rotations in opposite directions counterbalance resulting in a much weaker crystal orientation than expected from the SEM images. Noncavitating samples retain their translucency up to a high strain. © 2010 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 48: 1271–1280, 2010
Preparation of conducting poly(vinyl chloride)/polyindole composites and freestanding films via chemical polymerization
Authors: Taylan Naciye Bihter , Sari Bekir , Unal Halil Ibrahim
Published: May 2010

This study covers the synthesis of conducting polyindole (PIN) homopolymer, poly(vinyl chloride)/polyindole (PVC/PIN) composites, and preparation of their freestanding films. PIN and composites were synthesized chemically by radicalic mechanism using FeCl3 as an initiator. Films of PVC and PVC/PIN composites were prepared by casting on glass Petri dishes. Mechanical properties of films were examined by stress–strain experiments. From FTIR spectra of polymers, it was revealed that polymerization reaction occurred by 2–3 mechanism. The conductivities of polymers at different temperatures were also measured by four‐probe technique and found in the range 10−4 to 10−5 S cm−1. Magnetic properties of the polymers were analyzed by Gouy scale measurements and were found that their conducting mechanisms are of polaron and bipolaron natures. Thermal properties of polymers were investigated by differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA) and found that they had shown adequate thermal stability. X‐ray diffraction (XRD) spectra showed the amorphous nature of the polymers. Scanning electron microscopy (SEM) was used for microstructural analysis. © 2010 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 48: 1290–1298, 2010
Branched versus linear oligo(dimethylsiloxane): Differences in their thermodynamic interaction with solvents
Authors: Samadi Fatemeh , Eckelt John , Wolf Bernhard A. , Schüle Hanna , Frey Holger
Published: May 2010

The thermodynamic behavior of linear and of branched oligo(dimethylsiloxane) (O‐DMS) solutions was studied by means of vapor pressure measurements and vapor pressure osmometry at different temperatures for the thermodynamically favorable solvent THF. The branched material required for that purpose was synthesized and afterwards fractionated by means of the single solvent acetone to eliminate components of low degrees of branching. The Flory‐Huggins interaction parameters, χ, for the systems THF/O‐DMS as a function of composition pass a minimum at all temperatures (25, 40, and 60 °C) in the case of the branched material. For the unbranched oligomer such a minimum is only observed at 60 °C. At 40 °C the results are ambigous whereas the dependence is definitely linear at 25 °C. This exceptional behavior of the linear product at the latter temperature is tentatively attributed to the formation of favorable orientational order in the pure state under these conditions. At high oligomer concentrations THF interacts more favorably with the branched material, however, this preference is reversed upon dilution. All measured composition dependencies of χ can be modeled quantitatively by an approach accounting for chain connectivity and for the ability of the oligomers to change their conformation upon dilution. © 2010 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 48: 1309–1318, 2010
An NMR investigation on the phase structure and molecular mobility of the novel exfoliated polyethylene/palygorskite nanocomposites
Authors: Li Wei , Jiang Binbo , Buda Alina , Wang Jingdai , Blümich Bernhard , Yang Yongrong , Zheng Jie
Published: May 2010

Novel exfoliated polyethylene (PE)/palygorskite nanocomposites prepared by in situ polymerization are characterized by solid‐state nuclear magnetic resonance (NMR). The phase structure and molecular mobility are investigated by a combination of proton and carbon NMR. The results showed that incorporation of small amounts of palygorskite had great influence on the phase structure and molecular mobility. The incorporated palygorskite hindered the crystallization process and introduced motion‐hindered chains in the NMR crystalline and amorphous phase. 13C cross‐polarization and magic‐angle spinning NMR revealed two orthorhombic crystalline phase with different line‐width. The chain mobility of orthorhombic crystalline phase with broad resonance line is obviously hindered compared with the phase with narrow resonance line when the filler is introduced. Additionally, the results of pulsed field gradient NMR technique show those the tortuosities in the nanocomposites are much higher than that in the bulk PE. The self‐diffusion process of probe molecules is also influenced by the palygorksite load. © 2010 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 48: 1363–1371, 2010
Expression of proteinase‐activated receptor‐2 (PAR2) is androgen‐dependent in stromal cell line (hPCPs) from benign prostatic hyperplasia
Authors: Mannowetz Nadja , Würdinger Robert , Zippel Andrea , Aumüller Gerhard , Wennemuth Gunther
Published: May 2010

BACKGROUND

Growth properties of the prostate are regulated by a variety of hormones and growth factors. Benign prostatic hyperplasia (BPH) is characterized by abnormal epithelial and stromal proliferation. Varying androgen hormone levels in elderly men are correlated with abnormal proliferations of the prostate. Proteinase‐activated receptor‐2 (PAR2), a subtype of G‐protein‐coupled receptors, is known to induce multiple biological processes. It could also play a key role in the proliferation and metastasis of prostate cancer, but its effect on BPH pathogenesis is to a great extent unknown.

METHODS

Localization of PAR2 was determined both in pathologically altered and in normal prostate tissues by using immunohistochemical techniques. PAR2 activity was assessed by measuring changes in intracellular calcium [Ca2+]i following stimulation of cultured stromal cells with a PAR2 agonist (trypsin) and a synthetic PAR2‐activating peptide (AP). DHT‐dependence of PAR2 expression in prostate cancer and prostatic stromal cell lines was examined with semi‐quantitative and quantitative PCR. Cultured stromal cells (hPCPs) were stimulated with PAR2 AP and cell proliferation was determined through [3H]‐thymidine incorporation.

RESULTS

In comparison to normal prostate, PAR2 expression was increased in BPH stroma. DHT induced a higher expression of PAR2 when sub‐physiological DHT‐levels were used. Higher levels of DHT produced reduced PAR2 expression. A mitogenic effect was induced by applying PAR2 AP to hPCPs‐cells.

CONCLUSIONS

In conclusion, we found that PAR2 expression is hormone‐dependent in prostatic stromal cells with a negative correlation and we consider it to be an important factor in mitogenesis in BPH. Prostate 70:1350–1358, 2010. © 2010 Wiley‐Liss, Inc.
An in vitro model for preclinical testing of endocrine therapy combinations for prostate cancer
Authors: Pfeiffer Minja J. , Mulders Peter F. , Schalken Jack A.
Published: May 2010

BACKGROUND

Even though patients with prostate cancer commonly respond to endocrine treatment, in most cases the disease progresses to castration resistant prostate cancer (CRPC). Our objective was to generate a novel cell line model representing the endocrine treatment naive prostate cancer for testing treatments that target the androgen receptor (AR) and androgen metabolism.

METHODS

After culturing DuCaP cells 20 passages with additional 1 nM R1881, DuCaP‐N(aive) cell line was developed and validated for testing endocrine therapy combinations. Cell viability, apoptosis and cell cycle distribution were assessed in DuCaP and DuCaP‐N when interfering with the hormonal content.

RESULTS

Addition of 1 nM R1881 to DuCaP reduces cell viability and induces cell cycle inhibition and apoptosis. Eventually, an androgen accustomed DuCaP‐N cell line developed. An antiandrogen (bicalutamide), a histone deacetylase (HDAC) inhibitor (trichostatin A) and a 5α‐reductase (SRD5A) inhibitor (finasteride) reduce cell viability, and their combinations give a synergistic response in inducing apoptosis.

CONCLUSIONS

The TMPRSS2‐ERG expressing DuCaP‐N cell line represents human prostate cancer prior to endocrine treatment, and its parental DuCaP cell line is a model for CRPC. These cell lines can be used for preclinical evaluation of compounds that target the androgenic pathway. Prostate 70: 1524–1532, 2010. © 2010 Wiley‐Liss, Inc.
Thermodynamics of phosphotyrosine peptide–peptoid hybrids binding to the p56lck SH2 domain
Authors: Dekker F. J. , DE Mol N. J. , Liskamp R. M. J.
Published: May 2010

A frequently used approach to transform peptides into more drug‐like compounds is preparation of the corresponding peptoids or peptide–peptoid hybrids. Although peptoids have advantages, there may also be some disadvantages such as their increased flexibility and the reduced ability for hydrogen bond formation due to alkylation of the backbone amide nitrogen, which might affect the free Gibbs energy (ΔG). To obtain more insight into these contributions to ΔG, we performed thermodynamic analyses on the interaction between peptide–peptoid hybrids, based on the sequence ‐pTyr‐Glu‐Glu‐Ile‐, and the p56lck (Lck) Src homology 2 domain. van't Hoff analysis was performed on binding data obtained from surface plasmon resonance competition experiments in a temperature range of 10–40 °C. It is observed that amino acid–peptoid substitutions do not have a systemic negative effect on the entropic contributions to ΔG. However, loss in hydrogen‐bonding capacity of the backbone may strongly reduce the binding enthalpy and contribute to the observed lower binding affinity. Copyright © 2010 European Peptide Society and John Wiley & Sons, Ltd.
Optical phonons in colloidal CdSe nanorods
Authors: Lange Holger , Mohr Marcel , Artemyev Mikhail , Woggon Ulrike , Niermann Tore , Thomsen Christian
Published: May 2010

In this work the vibrational properties of colloidal CdSe nanorods (NRs) and CdSe‐ZnS core–shell NRs are investigated via Raman spectroscopy. The longitudinal optical (LO) phonons in NRs are confined to the NR volume. The confinement of the phonon wave function leads to a relaxation of the q = 0 rule and the phonon frequency is found to depend on the NR diameter. The coupling strength between LO phonons and excitons also depends on the NR diameter. The total coupling strength is much lower than in bulk material due to a decrease of the influence of the Coulomb interaction in nanoparticles. However, the coupling strength is found to rise for decreasing diameters. This is due to the increasing contributions of higher frequency phonons for smaller nanoparticle sizes. A radial breathing mode with a diameter dependent frequency is deduced from ab initio calculations and its existence in NRs is verified experimentally. The diameter‐dependence of the modes' frequency can be used to estimate the NR diameter from a Raman measurement. In core–shell structures, the lattice mismatch between core and shell leads to a compressive strain of the core lattice. The exciton wave function changes with the modified boundary. This is reflected in an altered exciton–phonon coupling strength.
Spontaneous polarization in III‐nitride materials: crystallographic revision
Authors: Karpov Sergey Yu.
Published: May 2010

A simple model for estimation of spontaneous polarization in III‐nitride compounds is suggested, utilizing the data on the materials lattice constants normally measured with sufficient accuracy. The model is applied to reconsider the spontaneous polarization in AlN, GaN, InN, and their alloys. The results are compared with those obtained by ab initio simulations. Polarization charges at the AlGaN/GaN and InGaN/GaN interfaces are calculated and compared with available data. The model can be easily extended to other wurtzite compounds and their alloys. (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Observation and quantification of the direction reversal of the surface band bending in GaAs1‐xNx using terahertz electromagnetic wave and photoreflectance measurements
Authors: Takeuchi Hideo , Yanagisawa Junichi , Hashimoto Jun , Nakayama Masaaki
Published: May 2010

We have investigated the polarity of terahertz (THz) electromagnetic waves from a GaAs1‐xNx epitaxial layer with x = 0.43% to clarify the effects of nitrogen incorporation on the direction of the surface band bending. The THz‐wave polarity of the GaAs1‐xNx sample is reversed compared with that of an i ‐GaAs/n ‐GaAs sample that has an upward surface band bending; namely, the GaAs1‐xNx sample has a downward band bending. The polarity reversal is attributed to the phenomenon that the conduction band bottom is lowered by the band anticrossing due to the nitrogen incorporation, which changes the direction of the surface band bending. We also measured the photoreflectance (PR) spectrum of the GaAs1‐xNx sample to quantify the surface electric field produced by the surface band bending. The PR spectrum exhibits the Franz‐Keldysh oscillations (FKOs) from the GaAs1‐xNx layer. From the FKOs, the surface electric field is estimated to be 24 kV/cm. (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Sublimation growth of bulk crystals of AlN‐rich (AlN)x(SiC)1–x solid solutions
Authors: Bickermann Matthias , Filip Octavian , Epelbaum Boris M. , Heimann Paul , Winnacker Albrecht
Published: May 2010

(AlN)x(SiC)1–x bulk single crystals are prepared by sublimation growth employing an AlN source placed in a tantalum carbide container. A 6H ‐SiC substrate acts both as seed and as source for silicon and carbon species. As the growth temperature is increased from 1900°C to 2050°C or the seed surface orientation is changed from (0115) to (0001), crystal coloration changes from yellowish to greenish to blackish. We attribute the change in coloration to an increasing Si/C content in the samples and estimate that up to 10% at of Si and C are incorporated. Accompanying changes in below band‐gap optical absorption and cathodoluminescence are discussed. (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Optical properties of bulk‐like GaN nanorods grown on Si(111) substrates by rf‐plasma assisted molecular beam epitaxy
Authors: Park Young S. , Kang T. W. , Im Hyunsik , Holmes Mark J. , Taylor Robert A.
Published: May 2010

We have investigated the optical properties of bulk‐like GaN nanorods by cathodoluminescence measurements at room temperature. The bulk‐like nanorods were grown on a Si (111) substrate by rf‐plasma assisted molecular beam epitaxy and are characterized be being surrounded by a compact region. A weak and broad emission line near 3.36 eV was observed at an accelerating voltage of 5 kV. This emission occurs at a lower energy than the emission from unstrained GaN nanorods that protrude from the compact region. Upon increasing the electron beam energy, and hence investigating regions deeper in the sample, the peak emission energy redshifts due to the strain at the substrate interface. The behaviour of the emission line is further investigated with cathodoluminescence measurement on single nanorod's (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Non‐equilibrium GaNAs alloys with band gap ranging from 0.8‐3.4 eV
Authors: Yu K. M. , Novikov S. V. , Broesler R. , Staddon C. R. , Hawkridge M. , Liliental‐Weber Z. , Demchenko I. , Denlinger J. D. , Kao V. M. , Luckert F. , Martin R. W. , Walukiewicz W. , Foxon C. T.
Published: May 2010

A new alloy system, the GaN1‐xAsx alloys in the whole composition range was successfully synthesized using the non‐equilibrium low temperature molecular beam epitaxy method. The alloys are amorphous in the composition range of 0.17 < x < 0.75 and crystalline outside this region. The amorphous films have smooth morphology, homogeneous composition and sharp, well defined optical absorption edges. The bandgap energy varies in a broad energy range from ∼3.4 eV in GaN to∼0.8 eV at x∼0.85. The reduction of the band gap can be attributed primarily to the downward movement of the conduction band for alloys with x > 0.2, and to the upward movement of the valence band for alloys with x < 0.2. (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
RF‐MBE growth of InN on 4H‐SiC (0001) with off‐angles
Authors: Orihara Misao , Takizawa Shin , Sato Takanori , Ishida Yuuki , Yoshida Sadafumi , Hijikata Yasuto , Yaguchi Hiroyuki
Published: May 2010

We have grown InN on 4H‐SiC (0001) substrates with various off‐angles by RF‐N2 plasma molecular beam epitaxy (RF‐MBE). Scanning electron microscope observation revealed that InN films grown on 4H‐SiC (0001) substrates with off‐angles of 4° and 8° are very smooth and that there are no voids which have often observed for InN epitaxial layers. X‐ray diffraction reciprocal space maps for InN grown on 4H‐SiC (0001) showed that the c‐axes of InN grown on 4H‐SiC 4° and 8° off substrates are inclined by 0.35° and 0.8°, respectively, toward the misorientation of the substrate while the c‐axis of InN is parallel to that of 4H‐SiC for the on‐axis substrate. Strong PL peak was observed from InN grown on 4° off substrate at 0.68 eV at 15 K. The PL peak was clearly observed even at room temperature and simply shifted to lower energies with increasing temperature. The difference in the PL peak energy between at 15 K and 300 K was 20 meV, which is reasonable taking into account the difference in the thermal coefficients of InN and SiC (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
The nucleation of HCl and Cl2‐based HVPE GaN on mis‐oriented sapphire substrates
Authors: Bohnen Tim , van Dreumel Gerbe W. G. , Weyher Jan L. , van Enckevort Willem J. P. , Ashraf Hina , de Jong Aryan E. F. , Hageman Paul R. , Vlieg Elias
Published: May 2010

The nucleation of both classic HCl‐based and novel Cl based HVPE GaN on mis‐oriented sapphire substrates was investigated. The use of Cl2in HVPE increases the growth rate by a factor of 4‐5 and strongly reduces the parasitic deposition, allowing for the growth of much thicker wafers than HCl‐based HVPE. Morphological SEM surface studies of the HCl‐based HVPE sample surface show that at 600 °C a nanocrystalline layer is deposited on the sapphire. During the subsequent annealing phase, the morphology changes to a μm‐sized island structure. During overgrowth at 1080 °C, the islands coalesce. Small voids or pinholes are then formed in between the coalescing GaN islands. These pinholes lead to numerous pits on the surface of the GaN at thicknesses of 5 μm. The pits disappear during continued overgrowth and can no longer be found on the surface, when the GaN film reaches a thickness of 45 μm. This particular coalescence mechanism also applies to Cl2‐based HVPE GaN on sapphire (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Photoelectrochemical application of GaN nanostructures on Si for hydrogen generation by water reduction
Authors: Fujii Katsushi , Kato Takashi , Sato Keiichi , Im Inho , Chang Jiho , Yao Takafumi
Published: May 2010

GaN nanostructures grown on n‐type Si (111) substrate were applied as photo‐illuminated working electrodes for photoelectrochemical water splitting. Photocurrent density increased with the density of GaN nanodots. The photocurrent density was, however, quite small compared to that of GaN nanorods and decreased with treated time. The current density of GaN nanorods was stable probably because the nanorod crystalline size was larger than that of the nanodots. (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Assessing consistent treatment effect in a multi‐regional clinical trial: a systematic review
Authors: Chen Joshua , Quan Hui , Binkowitz Bruce , Ouyang S. Peter , Tanaka Yoko , Li Gang , Menjoge Shailendra , Ibia Ekopimo ,   for the Consistency Workstream of the PhRMA MRCT Key Issue Team
Published: May 2010

A key issue in multi‐regional clinical trials (MRCTs) is how to assess the consistency of treatment effect across regions, although there is no a priori reason to believe that the treatment effect should vary across the regions. In this article, we define the research question as an assessment of overall consistency across all regions for which all regions are considered equally important. This is different from the region/country‐specific analyses (e.g. US vs Non‐US), which are frequently requested by local regulatory agencies and usually performed for multiple agencies. We provide a systematic review of methods that may potentially be used for assessing consistency across regions, including commonly used quantitative/qualitative interaction tests, Japanese Pharmaceutical Medical Device Agency (PMDA) Methods 1 & 2, and those proposed for different purposes (e.g. bridging studies, meta‐analysis, and vaccine lot consistency, among others). These methods are classified into three groups: global methods, multivariate quantitative methods, and multivariate qualitative methods. A case study is used to illustrate these methods. We also provide recommendations on how to choose appropriate methods and incorporate them in the study design. Copyright © 2010 John Wiley & Sons, Ltd.
Accurate mass measurement by matrix‐assisted laser desorption/ionisation time‐of‐flight mass spectrometry. I. Measurement of positive radical ions using porphyrin standard reference materials
Authors: Griffiths Nia W. , Wyatt Mark F. , Kean Suzanna D. , Graham Andrew E. , Stein Bridget K. , Brenton A. Gareth
Published: May 2010

A method for the accurate mass measurement of positive radical ions by matrix‐assisted laser desorption/ionisation time‐of‐flight mass spectrometry (MALDI‐TOFMS) is described. Initial use of a conjugated oligomeric calibration material was rejected in favour of a series of meso‐tetraalkyl/tetraalkylaryl‐functionalised porphyrins, from which the two calibrants required for a particular accurate mass measurement were chosen. While all measurements of monoisotopic species were within ±5 ppm, and the method was rigorously validated using chemometrics, mean values of five measurements were used for extra confidence in the generation of potential elemental formulae. Potential difficulties encountered when measuring compounds containing multi‐isotopic elements are discussed, where the monoisotopic peak is no longer the lowest mass peak, and a simple mass‐correction solution can be applied. The method requires no significant expertise to implement, but care and attention is required to obtain valid measurements. The method is operationally simple and will prove useful to the analytical chemistry community. Copyright © 2010 John Wiley & Sons, Ltd.