bluuebunny/crossref_metadata_2025_split huggingface dataset:
Poly(3‐chlorothiophene) films prepared by the direct electrochemical oxidation of 3‐chlorothiophene in mixed electrolytes of boron trifluoride diethyl etherate and sulfuric acid
Authors: Xu Jingkun , Shi Gaoquan , Chen Fengen , Wang Fan , Zhang Jiaxin , Hong Xiaoyin 
Published: November 2002

Abstract3‐Chlorothiophene (CT) was electrochemically polymerized in mixed electrolytes of a boron trifluoride diethyl etherate solution containing 0–20% (by volume) sulfuric acid. The oxidation potentials of the monomer in these media were measured to be only 1.06–1.31 V (vs Ag/AgCl). These values were much lower than that of CT in acetonitrile and 0.1 mol/L (Bu)4NBF4 (1.92 V vs Ag/AgCl). Poly(3‐chlorothiophene) (PCT) films with conductivities of 0.1–2 S cm−1 were obtained. The structure, morphology, and electrochemical behavior of the PCT films also were investigated. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 87: 502–509, 2003
Preparation and properties of poly(ethylene oxide) star polymers
Authors: Peppas Nicholas A. , Argade Ankush , Bhargava Saumitra 
Published: November 2002

AbstractPoly(ethylene oxide) (PEO) star polymers were prepared by anionic polymerization of methacryloyl chloride and glyceryl trimethacrylate with sec‐butyllithium in cyclohexane. The ensuing polymers were grafted with poly(ethylene glycol) of molecular weight 400. The final product was washed with methylene chloride and analyzed with infrared spectroscopy, differential scanning calorimetry, and thermogravimetry. Star polymers of PEO were also prepared by anionic polymerization of glycidol with sec‐butyllithium in cyclohexane. The initiator was chosen so as to yield a polymer of 10,000 molecular weight. The resulting polymers were analyzed by nuclear magnetic resonance, infrared spectroscopy, and thermogravimetry. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 87: 322–327, 2003
Graft copolymer–lanthanide complexes obtained by radiation grafting on polyethylene film
Authors: Choi Seong‐Ho , Lee Kwang‐Pill , Sohn Sang‐Ho 
Published: November 2002

AbstractRadiation‐induced grafting of acrylic acid (AAc) onto polyethylene (PE) film was investigated. The grafted films rapidly adsorbed Eu, Gd, Tb, and Dy ions at high efficiency. The carboxylic acid groups on the AAc‐grafted PE film acted as a chelating site for the selected lanthanide ions. Complex formation of lanthanide ions and the carboxylic acid group on PE film was investigated by IR, FT–Raman, and X‐ray photoelectron spectroscopy (XPS). Photoluminescence (PL) spectra and the thermal properties of the graft copolymer–lanthanide complexes onto PE film were also investigated. The application of such prepared graft copolymer–lanthanide complexes in the field of fluorescence emission displays (FEDs) may be interest. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 87: 328–336, 2003
Preparation and characteristics of composites of high‐crystalline cellulose with polypropylene: Effects of maleated polypropylene and cellulose content
Authors: Qiu Wulin , Zhang Farao , Endo Takashi , Hirotsu Takahiro 
Published: November 2002

AbstractBinary composites of high‐crystalline fibrous cellulose with polypropylene (PP) or maleic anhydride‐grafted polypropylene (MAPP) were prepared by melt‐mixing with different contents of cellulose from 0 to 60 wt %. Ternary composites of cellulose with PP and MAPP were also prepared to investigate the effects of MAPP as a compatibilizer between cellulose and PP. Scanning electron microscopy revealed that the addition of MAPP generates strong interactions between a PP matrix and cellulose fibers: All cellulose fibers are encapsulated by layers of the matrix and connected tightly within the matrix. Thus, the tensile strength and Young's modulus of MAPP‐containing composites increase with an increase in MAPP and cellulose content, in contrast to the decrease in tensile strength of a PP‐based binary composite with an increase in cellulose. Cellulose fibers act as a nucleating agent for the crystallization of PP, which is promoted by the addition of MAPP through an increase of the crystallization temperature of PP in the composite. Accordingly, both cellulose and MAPP facilitate the thermooxidative stability of PP composites in the following order: MAPP/cellulose > PP/MAPP/cellulose > PP/cellulose > PP. Relative water absorption increases with an increase in cellulose content, decreasing with the addition of MAPP. MAPP‐containing cellulose composites have high potential for applications as environmentally friendly materials. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 87: 337–345, 2003
Blends of i‐PP and SBS. II. Influence of in situ compatibilization on the mechanical properties
Authors: Wilhelm Helena Maria , Felisberti Maria Isabel 
Published: November 2002

AbstractThis article concerns the in situ compatibilization of immiscible isotatic polypropylene/styrene–butadiene–styrene triblock copolymer blends (i‐PP/SBS) by use of a reactive mixture. For this purpose, maleated PP (PP–MAH) and SBS (SBS–MAH) were used as functionalized polymers and 4,4′‐diaminediphenylmethane was used as a coupling agent between maleated polymers, resulting in a graft copolymer. Binary blends of i‐PP/SBS, nonreactive ternary blends of i‐PP/PP–MAH/SBS, and reactive ternary blends of i‐PP/PP–MAH/SBS–MAH with varying diamine/anhydride molar ratios were prepared. The mechanical properties of the blends were determined by tensile and impact‐resistance tests. The optimum improvement in the mechanical properties was found when the diamine/anhydride molar ratio in the ternary reactive blends was 0.5/1. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 87: 516–522, 2003
Investigation of plasma polymerized benzene and furan thin films for application in opto‐electronic devices
Authors: Jobanputra Manish C. , Durstock Michael F. , Clarson Stephen J. 
Published: November 2002

AbstractConjugated polymers are among the most promising organic materials for opto‐electronic devices. In such applications, the main fabrication problem is to get uniform, defect‐free, and reproducible thin films of these materials. In this investigation, an RF plasma reactor was used to produce cross‐linked organic thin films from benzene and furan precursors. Uniform thin films of desired thickness were fabricated using this plasma polymerization technique. The composition of the plasma‐polymerized films was determined with X‐ray photoelectron spectroscopy. Fourier transform infrared spectra of the monomers and plasma‐polymerized thin films prepared were compared to analyze the chemical structure of the films. Ultraviolet–visible absorption spectroscopy shows a red shift of 45 nm in λmax for the case of plasma‐polymerized benzene films and 52 nm in the case of plasma‐polymerized furan films when compared to their respective monomer spectra. Photo luminescence spectra of these films show a blue emission with a broad peak at 460 nm for the plasma‐polymerized benzene films and 445 nm for the plasma‐polymerized furan films. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 87: 523–528, 2003
Environmental stress cracking of poly(butylene succinate)/cellulose triacetate blend films
Authors: Tatsushima Tohru , Ogata Nobuo , Nakane Koji , Ogihara Takashi 
Published: November 2002

AbstractBlend films of poly(butylene succinate) (PBS) with cellulose triacetate (CTA) were prepared using a solvent‐cast technique. The environmental stress cracking (ESC) behavior of commercial PBS films and that of as‐prepared PBS/CTA blend films were investigated in an aqueous NaOH solution. It was found that the fracture behavior of PBS films can be analyzed by linear fracture mechanics, that is, the stress‐intensity factor, K, is found to control the crack‐growth rate, da/dt, in PBS films. The enhancement of da/dt induced by increasing the normality of NaOH(aq) is more marked at a high value of K rather than at a low value of K. Furthermore, the ESC behavior of the PBS/CTA blends was studied in NaOH(aq). It was found that the behavior cannot be analyzed by linear fracture mechanics and that the addition of CTA into PBS increases the ESC resistance of the blends. Large‐scale yielding of the material around the crack tip seems to be responsible for the high ESC resistance of the blends. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 87: 510–515, 2003
Graft copolymerization of methyl acrylate onto poly(vinyl alcohol) initiated by potassium diperiodatonickelate(IV)
Authors: Liu Yinghai , Liu Xiaohui , Deng Kuilin , Liu Zhanjun 
Published: November 2002

AbstractThe graft copolymerization of methyl acrylate onto poly(vinyl alcohol) (PVA) with a potassium diperiodatonickelate(IV) [Ni(IV)]–PVA redox system as an initiator was investigated in an alkaline medium. The grafting parameters were determined as functions of the temperature and the concentrations of the monomer and initiator. The structures of the graft copolymers were confirmed by Fourier transform infrared spectroscopy, scanning electron microscopy, X‐ray diffraction, differential scanning calorimetry, and thermogravimetric analysis. The Ni(IV)–PVA system was found to be an efficient redox initiator for this graft copolymerization. A single‐electron‐transfer mechanism was proposed for the formation of radicals and the initiation. Other acrylate monomers, such as methyl methacrylate, ethyl acrylate, n‐butyl acrylate, and n‐butyl methacrylate, were used as reductants for graft copolymerization. These reactions definitely occurred to some degree. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 87: 529–534, 2003
Electroactive mixtures of polyaniline and EPDM rubber: Chemical, thermal, and morphological characterization
Authors: Domenech S. C. , Bortoluzzi J. H. , Soldi V. , Franco C. V. 
Published: November 2002

AbstractA new route for blending polyaniline (PAni) and EPDM rubber was devised with maleic anhydride as a compatibilizer precursor. Rubber matrices containing ammonium peroxidisulfate and dodecyl benzene sulfonic acid were cast from organic solvents. Exposure to the monomer vapors allowed the chemical polymerization of aniline. The influence of PAni and the compatibilizer on the thermal properties, chemical structure, electrical conductivity, and morphology of the mixtures was observed with differential scanning calorimetry, thermogravimetric analysis, Fourier transform infrared, in situ conductivity measurements, and optical microscopy. The micrographs showed a good distribution of the PAni complex in the matrix. The use of approximately 2 wt % compatibilizer resulted in chemical interactions between maleic anhydride and the PAni complex formed with dodecyl benzene sulfonic acid, which could enhance the compatibility between the polymers. The obtained blends reached relative electrical conductivity values of up to 9 × 10−3 S cm−1. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 87: 535–547, 2003
Molar group contributions to polymer flammability
Authors: Walters Richard N. , Lyon Richard E. 
Published: November 2002

AbstractThe specific heat‐release rate is the molecular‐level fire response of a burning polymer. The Federal Aviation Administration obtains the specific heat‐release rate of milligram samples by analyzing the oxygen consumed by the complete combustion of the pyrolysis gases during a linear heating program. Dividing the specific heat‐release rate (W/g) by the rate of the temperature rise (K/s) of a sample during a test gives a material fire parameter with the units (J/g K) and significance of the heat (release) capacity. The heat‐release capacity appears to be a true material property that is rooted in the chemical structure of the polymer and is calculable from additive molar group contributions. Hundreds of polymers of known chemical compositions have been tested to date, providing over 40 different empirical molar group contributions to the heat‐release capacity. Measured and calculated heat‐release capacities for over 80 polymers agree to within ±15%, suggesting a new capability for predicting flammability from the polymer chemical structure. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 87: 548–563, 2003
Compatibilization of syndiotactic polystyrene and a thermotropic liquid‐crystalline polymer blend with a zinc salt of a sulfonated polystyrene ionomer
Authors: Son Younggon , Weiss R. A. 
Published: November 2002

AbstractA zinc salt of a lightly sulfonated (4.5 mol %) polystyrene ionomer was used to compatibilize a 3/1 (w/w) blend of syndiotactic polystyrene and a wholly aromatic thermotropic liquid‐crystalline polymer (TLCP). The addition of the ionomer significantly reduced the dispersed TLCP domain size and improved the tensile strength, ultimate elongation, and flexural toughness of the blend. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 87: 564–568, 2003
Effect of the physicochemical properties on the permeation performance in fully aromatic crosslinked polyamide thin films
Authors: Juhn Roh Il 
Published: November 2002

AbstractThin‐film‐composite reverse‐osmosis (RO) membranes were prepared by the interfacial polymerization of trifunctional 1,3,5‐benzentricarbonyl chloride (TMC) with difunctional 1,3‐benzendiamine (MPDA) or 1,4‐benzendiamine (PPDA). The meta‐positioned polyamide (MPDA/TMC) resulted in higher water flux but lower salt rejection than the para‐positioned polyamide (PPDA/TMC). To understand this behavior, we studied various factors including the thickness, rupture strength, chemical properties, and solubilities of the water and salt in the thin‐film polyamide. The thin films made from MPDA and PPDA possessed similar thicknesses and rupture strengths adequate for withstanding the RO operation pressure. However, the meta‐positioned polyamide had higher hydrophilicity and greater molecular chain mobility than the para‐positioned polyamide, resulting in higher water flux. In contrast, the para‐positioned polyamide had lower salt solubility and lower molecular chain mobility than the meta‐positioned polyamide, thereby possessing higher salt rejection. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 87: 569–576, 2003
Molecular dynamics simulation studies of induced fit and conformational capture in U1A–RNA binding: Do molecular substates code for specificity?
Authors: Pitici Felicia , Beveridge David L. , Baranger Anne M. 
Published: November 2002

AbstractMolecular dynamics (MD) simulations on stem loop 2 of U1 small nuclear RNA and a construct of the U1A protein were carried out to obtain predictions of the structures for the unbound forms in solution and to elucidate dynamical aspects of induced fit upon binding. A crystal structure of the complex between the U1A protein and stem loop 2 RNA and an NMR structure for the uncomplexed form of the U1A protein are available from Oubridge et al. (Nature, 1994, Vol. 372, pp. 432–438) and Avis et al. (Journal of Molecular Biology, 1996, Vol. 257, pp. 398–411), respectively. As a consequence, U1A–RNA binding is a particularly attractive case for investigations of induced fit in protein–nucleic acid complexation. When combined with the available structural data, the results from simulations indicate that structural adaptation of U1A protein and RNA define distinct mechanisms for induced fit. For the protein, the calculations indicate that induced fit upon binding involves a non‐native thermodynamic substate in which the structure is preorganized for binding. In contrast, induced fit of the RNA involves a distortion of the native structure in solution to an unstable form. However, the RNA solution structures predicted from simulation show evidence that structures in which groups of bases are favorably oriented for binding the U1A protein are thermally accessible. These results, which quantify with computational modeling recent proposals on induced fit and conformational capture by Leuillot and Varani (Biochemistry, 2001, Vol. 40, pp. 7947–7956) and by Williamson (Nature Structural Biology, 2000, Vol. 7, pp. 834–837) suggest an important role for intrinsic molecular architecture and substates other than the native form in the specificity of protein–RNA interactions. © 2002 Wiley Periodicals, Inc. Biopolymers 65: 424–435, 2002
Stability of protein‐bound conformations of bioactive peptides: The folded conformation of an epidermal growth factor‐like thrombomodulin fragment is similar to that recognized by thrombin
Authors: Song Jianxing , Xu Ping , Koutychenko Anatol , Ni Feng 
Published: November 2002

AbstractThe relationship between the free and bound conformations of bioactive peptides is explored using the epidermal growth factor (EGF)‐like thrombomodulin fragment hTM409–426 as a model system. The hTM409–426 peptide has a sequence of C409PEGYILDDGFIC421TDIDE (with a disulfide bond between Cys409 and Cys421) and is a selective inhibitor of thrombin. Upon binding to thrombin, hTM409–426 adopts a well‐defined conformation—namely, a β‐turn followed by an antiparallel β‐sheet, similar to those found in all other EGF‐like protein repeats (Hrabal et al., Protein Science, 1996, Vol. 5, 195–203). Here we demonstrate that, at pH 6.8 and at 25°C, the hTM409–426 peptide in the free state is very flexible, but still populates a type II β‐turn over residues Pro410–Glu411–Gly412–Tyr413 and the clustering of some hydrophobic side chains, both of which are present in the thrombin‐bound conformation. At a lower temperature of 5 °C, significant conformational shifts of the CαH proton resonances and extensive medium‐ and long‐range NOEs are observed, indicating the presence of folded conformations with unique backbone–backbone and side‐chain interactions. A comparison of the NOE patterns in the free state with transferred NOEs shows that the free‐state folded and the thrombin‐bound conformations of the hTM409–426 peptide are very similar, particularly over residues Pro410–Ile424. The folded conformation of hTM409–426 appears to be stabilized by two hydrophobic clusters, one formed by the side chains of residues Pro410, Tyr413, Leu415, and Phe419 and the Cys409–Cys421 disulfide bond, the second involving residues Ile414 and Ile424. These results indicate that the overall topology of the thrombin‐bound conformation of the hTM409–426 peptide is prefolded in the free state and the primary sequence (including the disulfide bond) may be selective for an ensemble of conformations similar to that recognized by thrombin. Published 2002 Wiley Periodicals, Inc. Biopolymers 65: 373–386, 2002
Probing multiple effects on 15N, 13Cα, 13Cβ, and 13C′ chemical shifts in peptides using density functional theory
Authors: Xu Xiao‐Ping , Case David A. 
Published: November 2002

AbstractWe have used density functional calculations on model peptides to study conformational effects on 15N, 13Cα, 13Cβ, and 13C′ chemical shifts, associated with hydrogen bonding, backbone conformation, and side‐chain orientation. The results show a significant dependence on the backbone torsion angles of the nearest three residues. Contributions to 15N chemical shifts from hydrogen bonding (up to 8 ppm), backbone conformation (up to 13 ppm), side‐chain orientation and neighborhood residue effects (up to 22 ppm) are significant, and a unified theory will be required to account for their behavior in proteins. In contrast to this, the dependence on sequence and hydrogen bonding is much less for 13Cα and 13Cβ chemical shifts (<0.5 ppm), and moderate for carbonyl carbon shifts (<2 ppm). The effects of side‐chain orientation are mainly limited to the residue itself for both nitrogen and carbon, but the χ1 effect is also significant for the nitrogen shift of the following residue and for the 13C′ shift of the preceding residue. The calculated results are used, in conjunction with an additive model of chemical shift contributions, to create an algorithm for prediction of 15N and 13C shifts in proteins from their structure; this includes a model to extrapolate results to regions of torsion angle space that have not been explicitly studied by density functional theory (DFT) calculations. Crystal structures of 20 proteins with measured shifts have been used to test the prediction scheme. Root mean square deviations between calculated and experimental shifts 2.71, 1.22, 1.31, and 1.28 ppm for N, Cα, Cβ, and C′, respectively. This prediction algorithm should be helpful in NMR assignment, crystal and solution structure comparison, and structure refinement. © 2002 Wiley Periodicals, Inc. Biopolymers 65: 408–423, 2002
Chain stiffness of heteropolysaccharide from Aeromonas gum in dilute solution by dynamic light scattering
Authors: Xu Xiaojuan , Zhang Lina , Nakamura Yo , Norisuye Takashi 
Published: November 2002

AbstractDynamic light scattering measurements have been made on 15 fractions of aeromonas (A) gum, an extracellular heteropolysaccharide produced by the strain Aeromonas nichidenii, with dimethylsulfoxide containing 0.2M lithium chloride as the solvent at 25°C. Data for the translational diffusion coefficient D covering a molecular weight range from 4.5 × 105 to 2.1 × 106 and ratios of the z‐average radius of gyration 〈s2〉z1/2 to the hydrodynamic radius RH (calculated with previous 〈s2〉z data) suggest that the polymer behaves like a semiflexible chain in this solvent similar to the stiffness of cellulose derivatives. Thus the D data are analyzed on the basis of the Yamakawa–Fujii theory for the translational friction coefficient of a wormlike cylinder by coarse‐graining the heteropolysaccharide molecule. Excluded‐volume effects are taken into account in the quasi‐two‐parameter scheme, as was done previously for 〈s2〉z and [η] (the intrinsic viscosity) of A gum in the same solvent. The molecular weight dependence of RH is found to be explained by the perturbed wormlike chain with a persistence length of 10 nm, a linear mass density of 1350 nm−1, an excluded‐volume strength parameter of 1.3 nm, and a chain diameter of 2.8 nm. These parameters are in substantial agreement with those estimated previously from 〈s2〉z and [η] data, demonstrating that the solution properties (D, 〈s2〉z, and [η]) of the heteropolysaccharide are almost quantitatively described by the current theories for wormlike chains in the molecular weight range studied. © 2002 Wiley Periodicals, Inc. Biopolymers 65: 387–394, 2002
Molecular structure of the outer bacterial membrane of Pseudomonas aeruginosa via classical simulation
Authors: Shroll Robert M. , Straatsma T. P. 
Published: November 2002

AbstractA detailed structural analysis has been performed of the outer bacterial membrane of Pseudomonas aeruginosa using a parameterized classical simulation model (R. D. Lins and T. P. Straatsma, Biophysical Journal, 2001, Vol. 81, pp. 1037–1046) with modest modifications. The structural analysis of the membrane is presented and newly discovered characteristics of the membrane are discussed. Simulations indicate that the relative contribution of different ligands to calcium ion coordination varies across the membrane, while maintaining a constant average coordination number of 6.1. Water penetrates the surface of the membrane to a depth of about 30 Å. The hydration of ions and phosphate groups is shown to depend on location within the membrane. A measure of saccharide residue orientation is defined and average orientations are presented. Saccharide residues possess varying degrees of motion with a trend of greater mobility at the membrane surface. However, their motion is limited and even in the membrane outer core region the average structure appears fairly rigid over a period of 1 ns. © 2002 Wiley Periodicals, Inc. Biopolymers 65: 395–407, 2002