bluuebunny/crossref_metadata_2025_split huggingface dataset:
Computational Quantum Chemistry for Free‐Radical Polymerization
Authors: Coote Michelle L. 
Published: January 2006

AbstractThis article describes the use of computational chemistry of study radical polymerization processes. A simplified introduction to the main principles of ab initio molecular orbital theory and density functional theory is provided in terms accessible to the nonspecialist reader. It is also shown how the resulting quantum‐chemical data are used in the calculation of reaction rates and partition functions. This is followed by a brief practical discussion of the accuracy and applicability of methods currently available for studying radical reactions. The article concludes with a description of some of the applications of quantum chemical calculations in the field of free‐radical polymerization, including the a priori prediction of rate coefficients, and the study and interpretation of structure‐reactivity trends. These studies illustrate the contribution that quantum chemistry has already made to our understanding of radical polymerization, and highlight its potential as a tool for solving further mechanistic problems in this field.
Surface Mechanical Damage and Wear of Polymers
Authors: Sinha S. K. , Briscoe B. J. 
Published: January 2006

AbstractThis chapter provides an up‐to‐date review of the current understanding in the area of mechanical damage and wear of polymer surfaces. Wear is explained by the two‐term friction model and classified as the interfacial (adhesive) wear and the cohesive (abrasive) wear. Further, distinction is made between other mechanisms that may occur in concurrence with the above two types. Two important such mechanisms are the chemical wear and the fatigue wear. Complexities associated with the microscopic events such as the stick‐slip phenomenon and with the lubrication aspect of polymers are also highlighted. Finally, a short review of the wear process encountered in the case of polymer composites is presented as composites have become the most popular and economic way of solving many of the industrial tribolgical problems where polymers are involved.
Cover Picture: Direction‐Dependent Homoepitaxial Growth of GaN Nanowires (Adv. Mater. 2/2006)
Authors: Li H. , Chin A. H. , Sunkara M. K. 
Published: January 2006

AbstractGaN nanowires with vastly different morphologies depending upon their growth direction can be produced by direct nitridation and vapor transport of Ga in disassociated ammonia, report Sunkara and co‐workers on p. 216. Nanowires grown along the c‐direction develop hexagonal‐prism island morphologies, while wires grown along the a‐direction form uniform, belt‐shaped morphologies. A “ballistic” phenomenon involving the 1D transport of adatoms on the non‐polar surfaces of <0001> GaN nanowires is proposed to explain the prismatic island morphologies.
Inside Front Cover: Experimental Evidence for Superprism Effects in Three‐Dimensional Polymer Photonic Crystals (Adv. Mater. 2/2006)
Authors: Serbin J. , Gu M. 
Published: January 2006

AbstractThe inside cover illustrates the highly dispersive propagation of light in a three‐dimensional polymer photonic crystal. White light is coupled into a woodpile structure and split into its wavelength components due to the frequency‐dependent dispersion properties of the structure. This superprism effect is orders of magnitudes higher than in a conventional glass prism and is caused by the strong anisotropy of the dispersion surface at frequencies slightly above the photonic bandgap. In work reported on p. 221, Serbin and Gu fabricated these woodpile structures operating in the near‐infrared wavelength range by means of two‐photon polymerization and give theoretical and experimental evidence for the superprism effect in these low‐index photonic‐crystal structures.
Kinetics of adsorption of sulfur mustard vapors on carbons under static conditions
Authors: Prasad G. K. , Singh Beer , Saxena Amit 
Published: January 2006

AbstractActivated carbon of surface area 1250 m2/g was impregnated with 4% sodium hydroxide plus 3% Cr(VI) as CrO3 with and without 5% ethylenediamine (EDA) and 5% ruthenium chloride by using their aqueous solutions. These carbons along with active carbon were studied for the adsorption of sulfur mustard (HD) under static conditions at 30 ± 1°C. Kinetics of adsorption have been studied by using the linear driving force model (LDF) and Fickian diffusion model. The kinetic parameters, such as equilibration constant/rate constant (ka), equilibration capacity, diffusional exponent (n), and adsorbate‐adsorbent interaction constant (K), have also been determined. The diffusional exponent being less than 0.5 indicates Fickian diffusion of HD molecules in the studied carbons. Chemical interaction also seems to be the second mechanism (although minor) and is involved in the HD uptake rate (the first being the Fickian diffusion). The adsorbate‐adsorbent interaction constant did not vary significantly, indicating that probably HD chemically interacts to a small extent with the metal salts present on the surface of active carbon as impregnants. © 2005 American Institute of Chemical Engineers AIChE J, 2006
Water‐gas shift reaction kinetics over μ‐structured Pt/CeO2/Al2O3 catalysts
Authors: Germani G. , Schuurman Y. 
Published: January 2006

AbstractPlatinum/ceria/alumina catalysts have been prepared in the microchannels of stainless steel platelets. These catalysts are very active for the water‐gas shift reaction between 250–400°C. The use of microreactors as kinetic devices has a clear advantage that the thin catalyst film allows the determination of the intrinsic kinetics even in the case of fast reactions. However, the channel design should be such that plug flow conditions are favored. The kinetics of the water‐gas shift reaction, free from internal diffusion limitations, have been studied over thin catalyst layers over a large range of operation conditions. The reaction rate is almost zero‐order in carbon monoxide and strongly inhibited by the partial pressure of hydrogen and to a lesser extent to that of carbon dioxide. An overall activation energy of 76.8 ± 2 kJ/mol has been measured. The data are best described by a dual‐site mechanism, where platinum provides an adsorption site for carbon monoxide and ceria an adsorption site for water. The rate‐determining step involves the formation of a complex between a carboxyl species and a hydroxyl group that decomposes over a free platinum site into carbon dioxide and hydrogen. © 2006 American Institute of Chemical Engineers AIChE J, 2006
Serinoctamere: Clusterbildung, Reaktionen und Auswirkungen auf die Homochiralität von Biomolekülen
Authors: Nanita Sergio C. , Cooks R. Graham 
Published: January 2006

AbstractNoch immer ist die Entwicklung der Homochiralität eines der spannendsten Rätsel im Zusammenhang mit der Entstehung des Lebens. Ein mögliches Szenario geht davon aus, dass Aminosäure‐Aggregate an einer Folge chemischer Ereignisse beteiligt waren, die zu chiralen Biomolekülen in sich selbst replizierenden Systemen und damit zur Homochirogenese führten. Serin steht als Aminosäure im Zentrum des Interesses, weil es ionische Cluster bildet, die sich aus der “magischen” Zahl von acht Aminosäureeinheiten zusammensetzen; diese Cluster zeigen eine auffällige Präferenz für Homochiralität. Die Serinoctamer‐Cluster (Ser8) können unter simulierten präbiotischen Bedingungen erzeugt werden, und sie reagieren enantioselektiv mit anderen Biomolekülen. Diese Beobachtungen führten zu der Hypothese, dass die Chiralität in der Natur ursprünglich auf Serin zurückgeht und durch chemische Reaktionen auf andere Aminosäuren, Saccharide und Peptide übertragen wurde. Der vorliegende Aufsatz bewertet kritisch die Chemie von Ser8‐Clustern und die Experimente, die ihre mögliche Rolle bei der Homochirogenese stützen.
Apoptolidin: Induktion von Apoptose durch einen Naturstoff
Authors: Daniel Peter T. , Koert Ulrich , Schuppan Julia 
Published: January 2006

AbstractDer Naturstoff Apoptolidin führt selektiv bei bestimmten Krebszelllinien zum programmierten Zelltod. Dieser auch als Apoptose bezeichnete Vorgang ist ein wichtiger zellbiologischer Mechanismus zur Regulation von Homöostase und Morphogenese. Apoptotische Fehlregulationen sind mit verschiedenen Krankheiten verknüpft, insbesondere Krebs. Der extrinsische Weg zur Apoptose führt über Todesliganden und Todesrezeptoren zur Aktivierung einer Caspase‐Kaskade, die den proteolytischen Abbau der Zellarchitektur bewirkt. Die intrinsisch ausgelöste Apoptose beginnt mit der Übermittlung von Schäden im Zellinnern an das Mitochondrium, das seine strukturelle Integrität verliert und ein Apoptosom bildet, das die Caspase‐Kaskade auslöst. Apoptoseregulierende Verbindungen sind von großer medizinischer Bedeutung. Viele Naturstoffe regulieren apoptotische Abläufe, so auch Apoptolidin. Die bekannten synthetischen Zugänge zu Apoptolidin werden in diesem Aufsatz beschrieben und verglichen. Weitere apoptoseregulierende Naturstoffe werden ebenfalls kurz vorgestellt.
Non‐catalytic anhydride curing of hydrogenated bisphenol‐A glycidyl ether with 1,2,4‐cyclohexanetricarboxylic anhydride and light emitting diode encapsulation
Authors: Morita Yasumasa , Sugino Hiroaki 
Published: January 2006

AbstractNoncatalytic anhydride curing of hydrogenated bisphenol‐A glycidyl ether (YX8000) using hydrogenated trimellic anhydride (1,2,4‐cyclohexanetricarboxylic anhydride, H‐TMAn) and methylhexahydrophthalic anhydride (MeHHPA) were studied. Differential scanning calorimetry data shows no exthothermal under 190°C using MeHHPA without catalyst because of the low reactivity. On the other hand, H‐TMAn had higher reactivity and it can be cured without catalyst. The effect of anhydride concentration both on curing and on properties was studied in detail. For example, the highest Tg was found when YX8000 : H‐TMAn = 100 : 75 or YX8000 : MeHHPA = 100 : 100. The highest curing exothermal was found at similar ratio. Following, the encapsulation of light emitting diode (LED) was prepared with two anhydrides. Surface volume decrease was observed with MeHHPA by its evaporation, but H‐TMAn gave flat surface. After thermal cycle test of these LED, H‐TMAn was found to have better crack resistance than MeHHPA. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 962–966, 2006
Acrylate/EVA reactive blends and semi‐IPN: Chemical, chemical–physical, and thermo‐optical characterization
Authors: Errico M. E. , Greco R. , Laurienzo P. , Malinconico M. , Viscardo D. 
Published: January 2006

AbstractIn the present work, blends between poly(methyl methacrylate) (PMMA) or its copolymer with butyl methacrylate P(MMA‐co‐BMA) and poly(ethylene‐co‐vinyl acetate) (EVA) rubbers obtained applying the reactive blending principles were deeply investigated to clarify the chemistry of the system. A copolymeric phase, which is created in situ, was isolated and its chemical structure was determined through NMR analysis. The blends were also crosslinked with a flexible dimethacrylate to realize semi‐interpenetrated networks. The blends were characterized for their properties of interest (mechanical and optical behaviors). Particularly, an accurate investigation of the optical properties as a function of the temperature was performed. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci, 2006
Homopolymer and copolymers of 4‐methacrylamidophenyl‐4‐methoxystyryl ketone with methyl methacrylate: Synthesis, characterization, reactivity ratios, and photocrosslinkable properties
Authors: Nanjundan S. , Jayakumar R. , Selvamalar C. S. Jone 
Published: January 2006

Abstract4‐Aminophenyl‐4‐methoxystyryl ketone (APMSK) was prepared by reacting 4‐aminoacetophenone and 4‐methoxybenzaldehyde in the presence of sodium hydroxide as base catalyst. The methacrylamide monomer, 4‐methacrylamidophenyl‐4‐methoxystyryl ketone (MPMSK), was synthesized by reacting APMSK with methacryloyl chloride in the presence of triethylamine. Free‐radical solution polymerization technique was used to prepare the homo‐ and copolymers of different feed compositions of MPMSK with methyl methacrylate in methyl ethyl ketone solution at 70°C, using benzoyl peroxide as the initiator. The polymers were characterized by UV, IR, 1H‐NMR, and 13C‐NMR spectral techniques. The reactivity ratios of both comonomers were calculated using Fineman–Ross, Kelen–Tüdös, extended Kelen–Tüdös, and a nonlinear error‐in‐variables model (EVM) method using a computer program, RREVM. The molecular weights (M̄w and M̄n) and polydispersity indices of the polymers were determined using size exclusion chromatography. The glass‐transition temperatures of the polymers were determined by differential scanning calorimetry. The thermal stability of the polymers was measured by thermogravimetric analysis in air. The photoreactivity of the polymers was studied in chloroform solutions in the presence and absence of various triplet sensitizers. The effect of concentration of homopolymer and composition of the copolymers on the rate of photocrosslinking of the polymers was investigated. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci, 2006
Characterization and adsorption properties of the chelating hydrogels derived from natural materials for possible use in the improvement of groundwater quality
Authors: Shawky H. A. , Ali A. El‐Hag , El Sheikh R. A. 
Published: January 2006

AbstractA new carrageenan based chelating copolymer sorbent was prepared by gamma radiation induced copolymerization and crosslinking of kappa‐carrageenan (k‐Car) and acrylic acid (AAc). The swelling characteristics of the prepared copolymer were investigated by studying the effect of time, pH, and ionic strength of the swelling medium. The sorption capacities of the chelating copolymer for Fe, Pb, Mn, Zn, Cu, Sr, Cd, and Al were 172, 202, 202, 216, 221, 230, 239, and 244 mg/g respectively. The Freundlich and Langmuir adsorption isotherms were used to validate the metal uptake data and heats of adsorption for the investigated metal ions were calculated. The re‐use experiment showed that the prepared hydrogel could be regenerated upto at least 10 times. Because of the promising data collected from bench scale experiments, the prepared copolymer was examined as chelating sorbent to improve the quality of some groundwater resources. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci, 2006
Synthesis of branched polyethylene by in situ polymerization of ethylene with combined iron catalyst and Ziegler–Natta catalyst
Authors: Lu Zhanxia , Zhang Zhicheng , Li Yang , Wu Chunhong , Hu Youliang 
Published: January 2006

Abstract2,6‐Bis(imino)pyridyl iron catalyst and traditional Ziegler–Natta catalyst were combined together as tandem catalytic system, activated with the mixture of TEA and MAO, and used for synthesis of branched polyethylene by in situ polymerization of ethylene. The branched polyethylene with branches from 8/1000C to 29/1000C was produced by adjusting reaction conditions: the amount of TEA, MAO, iron catalyst used, and reaction temperatures. Not only the short branches such as ethyl and butyl but also the longer branches (hexyl and longer than hexyl) were detected in the products. The products exhibited higher molecular weight and broader molecular weight distribution than those obtained from metallocene catalysts, which would provide the materials excellent mechanical properties and processability. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci, 2006
Dielectric behavior of three phase polyimide percolative nanocomposites
Authors: Devaraju Naga Gopi , Lee Burtrand I. 
Published: January 2006

AbstractThree phase ceramic–metal–plastic (cermetplas) percolative nanocomposite films were prepared using polyimide, as the matrix to prepare the composite films. Silver nanoparticles with a mean particle size of about 41 nm were prepared and used as the metal phase. Nanocomposites of barium titanate (BaTiO3) particles in polyimide matrix, with silver as metallic inclusion, were formulated using effective medium theory and percolation theory. The concentration and frequency dependence of dielectric permittivity (ε) and loss tangent (tan δ) measurements were reported and discussed for cermetplas below the percolation threshold. Experimental results for cermetplas show that a ε of above 500 can be achieved below the percolation. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci, 2006
Preparation and adsorption performance of a cellulosic‐adsorbent resin for copper(II)
Authors: Bao‐Xiu Zhao , Peng Wang , Tong Zheng , Chun‐yun Chen , Jing Shu 
Published: January 2006

AbstractThe adsorbent resin was prepared by grafting copolymerization of acrylic acid and acrylamide onto cellulose under microwave irradiation, and was applied to adsorb copper ions from wastewater. The influences of adsorption time, resin particle size, pH values, and temperature of solution on its adsorption performance were investigated. At the optimal adsorption conditions, adsorption ratio could get to 99.2% and the adsorption capability reached 49.6 mg/g. Furthermore, adsorption theory model was based and study showed that the physical adsorption was dominating and it accorded to Freundlich isotherm model. XPS of adsorbent resin complex was tested, which ensured the chelating groups onto adsorbent surface. Adsorbent resin could be regenerated using 8% NH3·H2O, which had good regeneration effect, and experiment showed that adsorption ratio could still keep over 90% when resin was regenerated seven times. So, heavy metal‐ions could be reclaimed from gel resin and the circulation of resources could be realized. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci, 2006
Effects of preparation conditions on the surface modification and performance of polyethersulfone ultrafiltration membranes
Authors: Mosqueda‐Jimenez Daniella B. , Narbaitz Roberto M. , Matsuura Takeshi 
Published: January 2006

AbstractThe impact that some membrane preparation steps had on ultrafiltration (UF) membrane characteristics and performance was studied. Polyethersulfone (PES) was employed as base polymer, while N‐methyl pyrrolidone (NMP) was used as a solvent, and polyvinylpyrrolidone (PVP) was used as a nonsolvent pore‐forming additive. The manufacturing variables studied were solvent evaporation time and membrane surface modification, using a fluorine‐based copolymer referred to as surface‐modifying macromolecule (SMM). The flat sheet membranes, prepared via phase inversion, were characterized using solute transport data, X‐ray photoelectron spectroscopy (XPS), and contact angle measurements. Membrane performance was evaluated via filtration test protocol that included a 6‐day filtration of concentrated river water. The flux reduction with time was modeled using single and dual mechanisms of fouling. The pore blockage/cake filtration model described better the behavior of the permeation rate along the experiments. Increasing the solvent evaporation time decreased the size of the pores and the permeation rate. However, it did not significantly affect the removal of the organic compounds naturally present in the river water used as feed. XPS and contact angle measurements proved that the short evaporation periods did not allow enough SMM migration to the surface to provoke a significant effect on the membrane performance. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci, 2006
Effects of the steam test on bonding strength of laminated veneer lumbers manufactured by using different adhesives
Authors: Uysal Burhanettin 
Published: January 2006

AbstractFailures in adhesion of wood particles or fiber in a composite board can result from several factors. Poor chemical and physical interfacial interactions between the wood surface and the resin and dissimilar swelling of resin and wood resulting from moisture sorption are two of the most important mechanisms of bond failure. This study was performed to determine how the adhesives affect shear strength of laminated veneer lumbers (LVL) manufactured from poplar, beech, pine, black sea fir, and quercus veneers, with phenol–formaldehyde (PF), poly(vinyl acetate) (PVAc), Desmodur‐VTKA (D‐VTKA), and urea–formaldehyde (UF) adhesives. The shear strength tests were done (based on BS EN 205) on the LVL, after being exposed to steam for 96‐h period, according to the procedure of the Turkish Standards (TS) 3639. From the shear strength test, it was found that the highest shear strength was obtained in beech control samples (not exposed to steam) with PVAc adhesive (15.8 N/mm2) and the lowest shear strength was obtained in poplar LVL with UF adhesive (4.24 N/mm2). Beech wood and VTKA and PVAc adhesives could be proposed for manufacturing of LVL used in wet conditions and exposed to shear strain. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci, 2006
Synthesis and characterization of photoluminescent conjugated polymer containing N‐(α‐naphthyl)‐carbazole unit
Authors: Feng Liheng , Zhang Caihong , Chen Zhaobin , Qin Anjun , Yuan Maosen , Bai Fenglian 
Published: January 2006

AbstractA novel luminescent conjugated polymer, poly[{9‐(α‐naphthyl)‐3,6‐divinylenecarbazolylene}‐alt‐co‐(1,4‐phenylene)] (PNVCP), bearing alternated 9‐(α‐naphthyl)‐carbazole and benzene units, was synthesized via a Wittig–Horner reaction. The solubility, thermal, and optical properties were investigated. It was soluble in common organic solvents, such as tetrahydrofuran and 1,2‐dichlororoethane. Thermogravimetric analysis and differential scanning calorimetry showed that the conjugated polymer exhibited good thermal stability up to 496°C with a glass‐transition temperature higher than 110°C. The photoluminescence properties were studied. The polymer emits blue light and the quantum yield is 93% in solution. The emission spectra exhibited an obvious solvent effect. With the increase of the polarity of the solvents, the fluorescence spectra changed obviously and appeared to be redshifted at room temperature. The redshift was more obvious in aromatic solvents than in aliphatic solvents. When N,N‐dimethylaniline was gradually added into the solution of the conjugated polymer, the emission intensity of the fluorescence decreased. In comparison, the emission intensity of the polymer showed invariability when 1,4‐dicyanobenzene was added into the polymer solution. Moreover, the fluorescence of the polymer could be effectively quenched by fullerene. Overall, the synthesized polymer is a potential candidate material for fabrication of polymeric light‐emitting devices. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 923–927, 2006
Synthesis and characterization of antibacterial polychelates of urea–formaldehyde resin with Cr(III), Mn(II), Fe(III), Co(II), Ni(II), Cu(II), and Zn(II) metal ions
Authors: Nishat N. , Ahmad Sharif , Tansir Ahamad Rahisuddin 
Published: January 2006

AbstractWe studied the reaction between urea and formaldehyde with the purpose of preparing new polychelates of Cr(III), Mn(II), Fe(III), Co(II), Ni(II), Cu(II), and Zn(II) metal ions. These compounds were characterized by elemental analysis, IR spectroscopy, 1H‐NMR, electronic spectroscopy, thermogravimetric analysis (TGA), and molar conductance measurements. The percentage of metal in all of the polychelates was found to be consistent with 1:1.5 (metal/ligand) stoichiometry. The thermal behaviors of these coordination polymers were studied by TGA in a nitrogen atmosphere up to 750°C. The TGA results reveal that the complexes had higher thermal‐resistance properties compared to the common urea–formaldehyde resin. The molar conductivity and magnetic susceptibility measurements of the synthesized polychelates confirmed the geometry of the complexes. The antibacterial activity of the polychelates was also investigated with agar diffusion methods. The antibacterial activity of these polychelates was found to be reasonably good compared with standard drugs, namely, ciprofloxacin, ampicillin, and kanamycin. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 928–936, 2006