bluuebunny/crossref_metadata_2025_split huggingface dataset:
Rigid‐rod polymeric fibers
Authors: Chae Han Gi , Kumar Satish 
Published: January 2006

AbstractThis paper traces the historical development of high temperature resistant rigid‐rod polymers. Synthesis, fiber processing, structure, properties, and applications of poly(p‐phenylene benzobisoxazole) (PBO) fibers have been discussed. After nearly 20 years of development in the United States and Japan, PBO fiber was commercialized with the trade name Zylon® in 1998. Properties of this fiber have been compared with the properties of poly(ethylene terephthalate) (PET), thermotropic polyester (Vectran®), extended chain polyethylene (Spectra®), p‐aramid (Kevlar®), m‐aramid (Nomex®), aramid copolymer (Technora®), polyimide (PBI), steel, and the experimental high compressive strength rigid‐rod polymeric fiber (PIPD, M5). PBO is currently the highest tensile modulus, highest tensile strength, and most thermally stable commercial polymeric fiber. However, PBO has low axial compressive strength and poor resistance to ultraviolet and visible radiation. The fiber also looses tensile strength in hot and humid environment. In the coming decades, further improvements in tensile strength (10–20 GPa range), compressive strength, and radiation resistance are expected in polymeric fibers. Incorporation of carbon nanotubes is expected to result in the development of next generation high performance polymeric fibers. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 100: 791–802, 2006
Synthesis and characterization of sodium alginate/acrylamide semi‐interpenetrating polymer networks
Authors: Şolpan Dilek , Torun Murat 
Published: January 2006

AbstractSodium alginate (NaAlg)/acrylamide (AAm) semi‐interpenetrating polymer networks (IPNs) were prepared with three different compositions, in which the NaAlg concentration was 1, 2, or 3% (w/v) in 50% (w/v) AAm solutions. These solutions were irradiated with a 60Co γ source at different doses. The conversion percentage was determined as follows. The NaAlg/AAm IPN hydrogels were immersed to swell in a solution of the desired pH (3–9) at 25°C. The swelling results at pHs 7.0 and 9.0 indicated that the NaAlg/AAm IPN hydrogel containing 3% NaAlg showed the maximum swelling percentage in water. The diffusion of water within the NaAlg/AAm IPN hydrogels was non‐Fickian in character. The diffusion coefficients of the NaAlg/AAm IPN hydrogels in water were calculated. The thermal properties of NaAlg, polyacrylamide, and NaAlg/AAm IPNs were determined. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100:335–342, 2006
Synthesis and swelling behavior of thermosensitive poly(N‐isopropyl acrylamide‐co‐sodium‐2‐acrylamido‐2‐methyl propane sulfonate) and poly(N‐isopropyl acrylamide‐co‐sodium‐2‐acrylamido‐2‐methyl propane sulfonate‐co‐glycidyl methacrylate) hydrogels
Authors: Emik Serkan , Gürdağ Gülten 
Published: January 2006

AbstractThe crosslinked copolymers and terpolymers of N‐isopropyl acrylamide (NIPAm) with sodium‐2‐acrylamido‐2‐methyl propane sulfonate (NaAMPS) and glycidyl methacrylate (GMA) were prepared in the presence of N,N′‐methylene bisacrylamide (NMBA) as crosslinker by free radical solution polymerization at 4°C. Potassium persulfate (KPS) and potassium bisulfide (KBS) were used as initiator and accelerator, respectively. While molar percentages of NaAMPS in copolymers feed were varied as 1, 2, and 3; NaAMPS and GMA were used in the molar percentages of 1 : 1, 2 : 2, and 3 : 3, respectively, for the terpolymer preparation. NMBA contents were kept constant as 1 or 1.5 mol % of total monomer moles in feed composition. The effects of the comonomer type, feed composition, and the crosslinker contents on the lower critical solution temperatures (LCST), equilibrium swelling values (Q) of polymers, swelling kinetics in water at room temperature, and deswelling kinetics at 55°C were investigated. The results indicated that the higher the NaAMPS content in NIPAm/NaAMPS copolymer, the higher the Q and water uptake rate, but less the water release rate. However, the presence of hydrophobic GMA comonomer in the terpolymer of NIPAm/NaAMPS/GMA decreased the Q values, it increased both the water uptake and the water release rates. It was also observed that NIPAm/NaAMPS and NIPAm/NaAMPS/GMA polymers exhibit continuous phase transition behavior between 40 and 50°C. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 428–438, 2006
Electrical properties of conventional polyimide films: Effects of chemical structure and water uptake
Authors: Deligöz H. , Yalcinyuva T. , Özgümüs S. , Yildirim S. 
Published: January 2006

AbstractA series of conventional polyimide (CPI) films, based on pyromellitic dianhydride (PMDA) and benzophenonetetracarboxylicdianhydride (BTDA), were prepared by a two step process, and their dielectrical constant, dielectrical loss, and DC conduction behaviors were studied at different frequencies and voltages. Their dielectrical breakdown voltage, water uptake, and solubility properties were also investigated. The effects of chemical structure and water uptake on the electrical properties of the films are discussed in detail. The dielectric constants of the CPI films vary between 2.93 and 3.72 at 1 MHz frequency and they are in the following decreasing order: BTDA‐DDS > BTDA‐DDE > PMDA‐DDS > PMDA‐DDE. The structure and thermal and oxidative stability of films were analyzed by FTIR‐ATR and TGA, respectively. The results showed that all CPI films have good insulating properties, such as high dielectric breakdown voltage, low dielectric constant with stability for long period of frequency, and low leakage density. Our results concerning electrical properties also suggest that electron hopping is responsible for AC conduction and Poole‐Frenkel mechanism is predominant for DC conduction of all CPI films. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 810–818, 2006
Biodegradable polymer made of styrene and N‐benzyl‐4‐vinylpyridinium chloride
Authors: Kawabata Nariyoshi , Kakimoto Chizuko , Ikeuchi Hisaya 
Published: January 2006

AbstractA copolymer of styrene with N‐benzyl‐4‐vinylpyridinium chloride (BVP), poly(styrene‐co‐N‐benzyl‐4‐vinylpyridinium chloride) (PST‐co‐BVP), was degradable by activated sludge in soil when the oligo‐styrene portion was sufficiently small. The degradation of the equimolar copolymer followed first‐order kinetics when the polymer sample was 1.0 or 0.5 g/kg and gave a half‐life of 5.6 days. The degradation of PST‐co‐BVP with a reduced BVP content did not follow first‐order kinetics under the aforementioned conditions but appeared to follow the kinetics when the amount of the polymer sample was sufficiently small. Under the ultimate conditions, the half‐life of PST‐co‐BVP that contained 10.6 mol % BVP was estimated to be 12.5 days, and the half‐life of PST‐co‐BVP that contained 5 mol % BVP was expected to be 30–40 days. The incorporation of 5 mol % BVP appeared sufficient for making PST‐co‐BVP substantially biodegradable if we did not expect exceptionally rapid degradation. PST‐co‐BVP was different from conventional polystyrene but possessed biodegradability. Random scission of the main chain much predominated over uniform scission from the end of the polymer chain in the biodegradation of PST‐co‐BVP. The cleavage of the main chain at BVP appeared predominant over that of oligo‐styrene. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 554–559. 2006
Supercritical CO2‐assisted synthesis of polystyrene/clay nanocomposites via in situ intercalative polymerization
Authors: Li Jianbo , Xu Qun , Peng Qi , Pang Maizhi , He Suqin , Zhu Chengshen 
Published: January 2006

AbstractCyclodextrins can form inclusion complexes with different molecules with the aid of their special chemical (molecular) structures. Physical and chemical properties of molecules can change after the formation of complex. This special feature enables the usage of dextrins in different industry areas. In this study, applicability of cylcodextrins in textile dyeing and washing processes was investigated. With this aim, β‐cyclodextrin was used in direct dyeing of cellulosic fabrics and in rinsing processes of direct dyed fabrics. Retarder/leveling effect of β‐cyclodextrin in dyeing process has been studied and the results were compared with that of a commercial product. In general, cyclodextrins were used in washing processes to remove the absorbed surfactants. It has been investigated whether this effect was the same for washing of dyed fabrics. Eight different direct dyes, for which the chemical structures are known, were used in dyeing and washing processes, and effect of β‐cyclodextrin on different chemical structures was investigated. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 208–218, 2006
Effects of reaction and cure temperatures on morphology and properties of poly(ester‐urethane)
Authors: Zeng Ming , Zhang Lina 
Published: January 2006

AbstractPoly(ester‐urethane) was synthesized from poly(ethylene glycol adipate) (PEG) and 2,4‐toluene diisocyanate (TDI) to study the effects of reaction temperature and cure temperature on the crystallization behavior, morphology, and mechanical properties of the semicrystalline polyurethane (PU). PEG as soft segment was first reacted with TDI as hard segment at 90, 100, and 110°C, respectively, to obtain three kinds of PU prepolymers, coded as PEPU‐90, PEPU‐100, and PEPU‐110. Then the PU prepolymers were crosslinked by 1,1,1‐tris (hydroxylmethyl) propane (TMP) and were cured at 18, 25, 40, 60, and 80°C. Their structure and properties were characterized by attenuated total reflection Fourier transform infrared, wide‐angle X‐ray diffraction, scanning electron microscopy, dynamic mechanical analysis, and tensile testing. With an increase of the reaction temperature from 90 to 100°C, the crystallinity degree of soft segment decreased, but interaction between soft and hard segments enhanced, leading to the increase of the glass transition temperature (Tg) of soft domain and tensile strength. When the cure temperature was above 60°C, miscibility between soft and hard segments of the PEPU films was improved, resulting in relatively low crystallinity and elongation at break, but high soft segment Tg and tensile strength. On the whole, all of the PEPU‐90, PEPU‐100, and PEPU‐110 films cured above 60°C possessed higher tensile strength and elongation at break than that of the films cured at other temperatures. The results revealed that the reaction temperature and cure temperature play an important role in the improvement of the crosslinking structure and mechanical properties of the semicrystalline PU. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 708–714, 2006
Hydroxyalkylation of 6‐aminouracil
Authors: Chmiel‐Szukiewicz Elżbieta 
Published: January 2006

AbstractReactions of 6‐aminouracil with formaldehyde, ethylene and propylene oxide, and ethylene carbonate were studied. Hydroxyalkyl derivatives of 6‐aminouracil were prepared. The structure of the products were established by elemental analysis, 1H‐NMR, and IR techniques. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 715–719, 2006
Long‐term changes in the fish assemblage of the Laja River, Guanajuato, central Mexico
Authors: Mercado‐Silva Norman , Lyons John , Díaz‐Pardo Edmundo , Gutiérrez‐Hernández Altagracia , Ornelas‐García Claudia Patricia , Pedraza‐Lara Carlos , Zanden M. Jake Vander 
Published: January 2006

Abstract
The structure and composition of fish communities in rivers of central Mexico have been altered as a result of water over‐exploitation, habitat fragmentation, introduction of exotic species, and pollution. However, the specific pattern and degree of change are poorly documented.
Long‐term information from the Laja River (Guanajuato, Mexico) in the Lerma River basin was used to explore trends in fish species richness and community composition (species origin, trophic niche, tolerance, and preferred habitat) from the 1960s to the present in both river and reservoir sites.
Declines in native, sensitive, benthic native and carnivore species ranging from 11% to 30% per decade, and increases in the number of tolerant and exotic species by 9–20% per decade, are documented. Repeated measures ANOVA and sign tests revealed significant declines in the number of benthic, native, carnivore and sensitive species. Species richness, number of exotics, tolerant species and omnivore species did not change statistically, though statistical power was low. Some important changes occurred in these variables, such as the expansion and establishment of exotics such as Xiphophorus variatus and Micropterus salmoides, which pose a serious potential threat to native species.
The changes in fish community composition for the Laja portray how the fish communities in other rivers in central Mexico, for which long‐term data do not exist, have changed or could change if environmental deterioration continues.
Copyright © 2006 John Wiley & Sons, Ltd.
Laser‐scanning lithography (LSL) for the soft lithographic patterning of cell‐adhesive self‐assembled monolayers
Authors: Miller Jordan S. , Béthencourt Mathilde I. , Hahn Mariah , Lee T. Randall , West Jennifer L. 
Published: January 2006

AbstractWe report the development of laser‐scanning lithography (LSL), which employs a laser‐scanning confocal microscope to pattern photoresists that can be utilized, for example, in the fabrication of masters for use in soft lithography. This convenient technique provides even exposure across the entire view field and facilitates accurate alignment of successive photoresist exposures. Features on the scale of 3 µm have been achieved to date with a 10× objective (NA 0.45). Virtual masks, instructions for laser irradiation, were drawn using the Region of Interest (ROI) function of a Zeiss LSM 510 microscope. These regions were then exposed to a 458 nm argon laser for 32 µs (0.9 mW/µm2). Differential interference contrast (DIC) imaging was utilized with a non‐destructive 514 nm argon laser as an immediate quality check of each exposure, to align successive exposures, and to reduce chromatic aberration between imaging and exposure. Developed masters were replica‐molded with poly(dimethylsiloxane) (PDMS); these masters were then utilized for microcontact printing of cell‐adhesive self‐assembled monolayers (SAMs) to demonstrate the utility of this process. Initial studies confirmed that human dermal fibroblast adhesion and spreading were limited to cell‐adhesive SAM areas. LSL is a rapid, flexible, and readily available technique that will accelerate master design and preparation; moreover, it can be applied to additional forms of photolithography and photopolymerization for studies in cell biology, biomaterials design and evaluation, materials science, and surface chemistry. © 2006 Wiley Periodicals, Inc.
Altering the Regioselectivity of Cytochrome P450 CYP102A3 of Bacillus subtilis by Using a New Versatile Assay System
Authors: Lentz Oliver , Feenstra Anton , Habicher Tilo , Hauer Bernhard , Schmid Rolf D. , Urlacher Vlada B. 
Published: January 2006

AbstractA novel monooxygenase (CYP102A3) has been discovered within the Bacillus subtilis genome that reveals a similarity of 76 % to the well‐known cytochrome P450 BM‐3 of B. megaterium (CYP102A1). Both enzymes are natural fusion proteins consisting of a heme domain and a FAD/FMN‐reductase domain. Because of their high turnover rates, these biocatalysts are of special interest for industrial applications, but show only limited regioselectivity. In this work, the regioselectivity of CYP102A3 was changed by directed evolution and protein design to hydroxylate substrates not only in different subterminal, but also to a high extent, in terminal carbon chain positions. To enable a high‐throughput screening procedure, a very versatile assay was developed that is capable of discriminating between terminal and subterminal hydroxylation of carbon chains. A double mutant of CYP102A3 was obtained that produces 48 % octan‐1‐ol as the main product of the reaction.
Production of Lewis x Tetrasaccharides by Metabolically Engineered Escherichia coli
Authors: Dumon Claire , Bosso Claude , Utille Jean Pierre , Heyraud Alain , Samain Eric 
Published: January 2006

AbstractTwo tetrasaccharides carrying the trisaccharidic Lewis x motif on a GlcNAc or a Gal residue were produced on the gram‐scale by high‐cell‐density cultures of metabolically engineered Escherichia coli strains that overexpressed the Helicobacter pylori futA gene for α‐3 fucosyltransferase and the Neisseria meningitidis lgtB gene for β‐4 galactosyltransferase. The first compound Galβ‐4(Fucα‐3)GlcNAcβ‐4GlcNAc was produced by glycosylation of chitinbiose, which was endogenously generated in the bacterial cytoplasm by the successive action of the rhizobial chitin‐synthase NodC and the Bacillus circulans chitinase A1, whose genes were additionally expressed in the E. coli strain. The second compound, Galβ‐4(Fucα‐3)GlcNAcβ‐3Gal, was produced from exogenously added Gal by a strain that was deficient in galactokinase activity and overexpressed the additional N. meningitidis lgtA gene for β‐3 N‐acetylglucosaminyltransferase.
Genetic Targeting of Individual Cells with a Voltage‐Sensitive Dye through Enzymatic Activation of Membrane Binding
Authors: Hinner Marlon J. , Hübener Gerd , Fromherz Peter 
Published: January 2006

AbstractOptical recording of the electrical activity of individual neurons in culture or in a tissue requires cell‐selective staining with a fluorescent voltage‐sensitive dye. In a proof‐of‐principle experiment, we implement a novel approach to genetically targeted staining. The method relies on a water‐soluble precursor dye and an overexpressed cell‐surface enzyme that transforms the precursor into a hydrophobic dye that binds to the targeted cell. We fused an alkaline phosphatase to a specifically designed general‐purpose membrane anchor, and the fusion protein was expressed on the surface of HEK293 cells, as was corroborated by immuno‐ and histochemical staining. We next synthesised an amphiphilic hemicyanine dye containing two enzymatically cleavable phosphate groups at its hydrocarbon tails. When the phosphate groups were removed, the binding to membranes was enhanced by a factor of a thousand, as shown by titration with lipid vesicles. We observed selective staining of enzymatically active cells by fluorescence microscopy in a mixed population of phosphatase‐transfected and untransfected HEK293 cells. The critical parameters of enzyme‐induced cell‐selective staining were elucidated by a simple kinetic model to guide further developments of the method.
Fluorine Segregation in Crystalline Materials: Structural Control and Solid‐State [2+2] Cycloaddition in CF3‐Substituted Tetrathiafulvalene Derivatives
Authors: Jeannin Olivier , Fourmigué Marc 
Published: January 2006

AbstractThe well‐known influence of long perfluorinated chains on the structures and stability of amphiphilic molecules in liquid crystalline mesophases or mesoscopic micellar arrangements is evaluated here in the realm of crystalline materials based on rigid aromatic molecules bearing only a limited number of CF3moieties. Tetrathiafulvalene (TTF) derivatives bearing one or two CF3groups, that is, (Z)‐ and (E)‐(CF3)2TTF ((Z)‐1, (E)‐1), EDT‐TTF‐CF3(2), and EDT‐TTF(CF3)2(3) (EDT=ethylenedithio) are prepared from the 1,3‐dipolar reaction of methyl 4,4,4‐trifluorotetrolate with ethylenetrithiocarbonate. The structures of neutral (Z)‐1, (E)‐1,2,and3as indicated by single‐crystal X‐ray diffraction measurements reveal the recurrent formation of layered structures with a strong segregation of the fluorinated moieties and formation of fluorous bilayers, attributed to the amphiphilic character of those TTF derivatives upon CF3functionalization, and without need for longer CnF2n+1(n>1) perfluorinated chains. The short intermolecular distance between outer CC double bonds observed in the layered structure of (E)‐1allows a solid‐state [2+2] photocyclization with formation of chiral dyads incorporating the characteristic cyclobutane ring. These dyads containing two dihydrotetrathiafulvalene moieties facing each other exhibit reversible oxidation to the mixed‐valence radical cation state and organize in the solid‐state into the same layered structures with fluorous bilayers.
Catalytic Enantioselective Three‐Component Hetero‐[4+2] Cycloaddition/Allylboration Approach to α‐Hydroxyalkyl Pyrans: Scope, Limitations, and Mechanistic Proposal
Authors: Gao Xuri , Hall Dennis G. , Deligny Michael , Favre Annaick , Carreaux François , Carboni Bertrand 
Published: January 2006

AbstractThis article describes the design and optimization of a catalytic enantioselective three‐component hetero‐[4+2] cycloaddition/allylboration reaction between 3‐boronoacrolein, enol ethers, and aldehydes to afford α‐hydroxyalkyl dihydropyrans. The key substrate, 3‐boronoacrolein pinacolate (2) was found to be an exceptionally reactive heterodiene in the hetero‐[4+2] cycloaddition catalyzed by Jacobsen's chiral CrIII catalyst 1. The scope and limitations of this process were thoroughly examined. The adduct of 3‐boronoacrolein pinacolate and ethyl vinyl ether was obtained in high yield and with over 95 % enantioselectivity. This cyclic α‐chiral allylboronate adds to a very wide variety of aldehyde substrates, including unsaturated aldehydes and α‐chiral aldehydes to give diastereomerically pure products. Acyclic 2‐substituted enol ethers can be employed, in which case the catalyst promotes a kinetically selective reaction that favors Z enol ethers over the E isomers. Surprisingly, 3‐boronoacrolein pinacolate was found to be a superior heterodiene than ethyl (E)‐4‐oxobutenoate, and a mechanistic interpretation based on a possible [5+2] transition state is proposed.
Ruthenium‐Catalyzed Asymmetric Epoxidation of Olefins Using H2O2, Part I: Synthesis of New Chiral N,N,N‐Tridentate Pybox and Pyboxazine Ligands and Their Ruthenium Complexes
Authors: Tse Man Kin , Bhor Santosh , Klawonn Markus , Anilkumar Gopinathan , Jiao Haijun , Döbler Christian , Spannenberg Anke , Mägerlein Wolfgang , Hugl Herbert , Beller Matthias 
Published: January 2006

AbstractThe synthesis of chiral tridentate N,N,N‐pyridine‐2,6‐bisoxazolines 3 (pybox ligands) and N,N,N‐pyridine‐2,6‐bisoxazines 4 (pyboxazine ligands) is described in detail. These novel ligands constitute a useful toolbox for the application in asymmetric catalysis. Compounds 3 and 4 are conveniently prepared by cyclization of enantiomerically pure α‐ or β‐amino alcohols with dimethyl pyridine‐2,6‐dicarboximidate. The corresponding ruthenium complexes are efficient asymmetric epoxidation catalysts and have been prepared in good yield and fully characterized by spectroscopic means. Four of these ruthenium complexes have been characterized by X‐ray crystallography. For the first time the molecular structure of a pyboxazine complex {2,6‐bis‐[(4S)‐4‐phenyl‐5,6‐dihydro‐4H‐[1,3]oxazinyl]pyridine}(pyridine‐2,6‐dicarboxylate)ruthenium (S)‐2 aa, is presented.