bluuebunny/crossref_metadata_2025_split huggingface dataset:
Agostic Interactions in d0Metal Alkyl Complexes
Authors: Scherer Wolfgang , McGrady G. Sean 
Published: March 2004

AbstractThe phenomenon of agostic interactions is reviewed and the nature of the interaction is revisited. A historical perspective is followed by an overview of experimental techniques used to diagnose agostic behavior, and previous interpretations of agostic bonding are presented. A series of simple metal alkyl complexes is considered and a new model for the phenomenon in d0systems is developed which sets them apart from agostic late‐transition‐metal complexes. Factors such as the valence electron count and coordination number of the metal center are revealed to be unimportant in facilitating the interaction in most d0systems. The charge density distribution in several transition‐metal alkyl complexes is explored by experimental and theoretical techniques, including the powerful “Atoms in Molecules” approach. Local charge concentrations are shown to play an important role in the agostic interaction. Finally, we demonstrate for the first time a way to manipulate and control the magnitude and disposition of such local charge concentrations, and hence the strength of agostic interactions in d0metal alkyl complexes.
Crystallographic report: (2,2′‐Bipyridine)bis(N,N‐dibenzyldithiocarbamato)zinc(II)
Authors: Lai Chian Sing , Tiekink Edward R. T. 
Published: March 2004

AbstractThe structure of Zn[S2CN(CH2Ph)2]2(2,2′‐bipy) features a distorted trigonal prismatic geometry around the zinc centre defined by an N2S4 donor set; the molecule has two‐fold symmetry. Copyright © 2004 John Wiley & Sons, Ltd.
Crystallographic report: Bis(2‐diphenylglycolato‐O)bis(1,10‐phenanthroline‐N,N′)zinc(II), [Zn(C14H11O3)2(C12H8N2)2]
Authors: Carballo Rosa , Covelo Berta , García‐Martinez Emilia , Vázquez‐López Ezequiel M. , Castiñeiras Alfonso 
Published: March 2004

AbstractThe structure of [Zn(HB)2(1,10‐phen)2] (HB = diphenylglycolato) comprises mononuclear molecules with the zinc(II) cation situated on a two fold axis and octahedrally coordinated by an N4O2 donor set. Copyright © 2004 John Wiley & Sons, Ltd.
Synthesis and neurotropic activity of silyl propargyl alcohols and sulfides
Authors: Abele Ramona , Zvejniece Liga , Abele Edgars , Rubina Kira , Arsenyan Pavel , Vandish Marina , Pudova Olga , Dambrova Maija , Domracheva Ilona , Shestakova Irina , Popelis Juris , Lukevics Edmunds 
Published: March 2004

AbstractNew silicon derivatives of hetaryl propargyl sulfides and propargyl alcohols were synthesized using phase‐transfer catalytic and organometallic methods. These compounds were tested for acute toxicity and neurotropic activity in the pentylenetetrazole test, and for phenamine hypothermia, phenamine hyperactivity and passive avoidance response tests. We have found that the silyl propargyl alcohols and sulfides are low toxicity compounds, the LD50 being 700–1300 mg kg−1. In the PAR test, the synthesized compounds exerted some memory‐improving activity. For di‐1‐(3‐methyl‐3‐hydroxybutyn‐1‐yl)methyl(3‐iodopropyl)silane (16) the effect was statistically significant and amounted to 250% of the control level. In the pentylenetetrazole test, all compounds possessed anticonvulsant activity, the most active compounds being 3‐(benzoxazolylthio)‐1‐propynyl(trimethyl)silane (6) and di‐[2‐(1‐hydroxycyclohexyl)ethynyl]methyl(3‐iodopropyl)silane (17). The phenamine‐induced hyperactivity was significantly elevated after treatment with (3‐trimethylsilyl‐2‐propynyl)thiobenzene (1) or di‐[1‐(3‐methyl‐3‐hydroxybutyn‐1‐yl)diphenylsilane (12). Our data show that these silicon derivatives of hetaryl propargyl sulfides and propargyl alcohols possess certain memory improving and anticonvulsant activity that should be studied in detail to evaluate the receptor systems involved. Copyright © 2004 John Wiley & Sons, Ltd.
Review: Synthetic methodologies in siloxanes
Authors: Purkayastha Arup , Baruah Jubaraj Bikash 
Published: March 2004

AbstractThis review describes the various types and synthetic strategies for the production of siloxanes. A description is given of the various synthetic methods for the production of organic compounds with silicon–oxygen bonds. The different types of siloxane are described, with the emphasis being on their structural aspects. Copyright © 2004 John Wiley & Sons, Ltd.
Synthesis, characterization and cytotoxicity of some triarylbismuth(V) di(N‐p‐toluenesulfonyl) aminoacetates and the crystal structure of (4‐CH3C6H4SO2NHCH2CO2)2Bi(C6H4Cl‐4)3
Authors: Yu Lin , Ma Yong‐Qiang , Wang Guo‐Cang , Song Hai‐Bin , Wang Hong‐Geng , Li Jin‐Shan , Cui Jing‐Rong , Wang Rui‐Qing 
Published: March 2004

AbstractA series of triarylbismuth(V) di(N‐p‐toluenesulfonyl)aminoacetates with the formula (4‐CH3C6H4SO2NHCH2CO2)2BiAr3 (ArC6H5, 4‐CH3C6H4, 4‐ClC6H4, 4‐BrC6H4) were synthesized and characterized by elemental analysis, IR, 1H NMR and mass spectra. The crystal structure of (4‐CH3C6H4SO2NHCH2CO2)2Bi(C6H4Cl‐4)3 was determined and shows the bismuth to exist in a distorted trigonal bipyramidal geometry. Four human neoplastic cell lines (HL‐60, PC‐3MIE8, BGC‐823 and MDA‐MB‐435) were used to screen these compounds. The results indicate that these compounds at 10 μM show cytotoxicity. Copyright © 2004 John Wiley & Sons, Ltd.
Natural rubber–isotactic polypropylene thermoplastic blends
Authors: Varghese Siby , Alex Rosamma , Kuriakose Baby 
Published: March 2004

AbstractThermoplastic elastomers, prepared by melt blending of natural rubber (NR) and isotactic polypropylene (PP) through a dynamic vulcanization technique, were developed during the later 1970s. However, they have certain drawbacks due to thermal degradation and higher molecular weight of NR. In the study reported here, NR was masticated to different levels prior its addition to isotactic polypropylene to improve the flow properties and to reduce the incompatibility resulting from molecular weight mismatch of NR/PP thermoplastic blends. Mixing energy curves of uncrosslinked blends and those of dynamically vulcanized blends crosslinked using different cure systems were compared. The mixing energy curves of blends containing NR of different molecular weight (Mn) and two grades of PP (injection and film grades) were also compared. Technological and processing properties of the dynamically vulcanized (sulphur and peroxide cure systems) and unvulcanized blends were compared with those of the samples containing unmasticated NR. The results indicated that a number average molecular weight in the range 4 × 105 for NR increased the procoessability without significantly affecting the technological properties of NR/PP thermoplastic blends. Among the three cure systems studied Luperox 101 and dicumyl peroxide gave better technological properties than the sulphur‐cured samples. Two antioxidants, viz. quinoline (TDQ) and imidazole (MBI) type, were tried in NR/PP blends. It was found that TDQ imparts better aging resistance compared to MBI. The improvement in processability due to the reduction in molecular weight of natural rubber by mastication is more noticeable in the case of peroxide vulcanized blends compared to sulphur vulcanized samples. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 2063–2068, 2004
Hydrophobic properties of ethylene–vinyl alcohol copolymer treated with plasma source ion implantation
Authors: Kim Kibeom , Sung Woonmo , Park Hyunjin , Lee Yeonhee , Han Seunghee , Kim Wangjune 
Published: March 2004

AbstractThe industrial use of ethylene–vinyl alcohol copolymer (EVOH) film is limited because it is easily degraded by moisture. The plasma source ion implantation (PSII) technique with CF4 or CH4 gas was used for the EVOH film to improve the surface hydrophobic properties. Variables examined in implantation were ion energy (0–10 keV), treatment time (5 s–5 min), and ion species. The hydrophobic properties of EVOH films were greatly enhanced after a CF4 PSII treatment, as evidenced by an increased contact angle from 66° to above 100° at ‐5 keV, and remained relatively unchanged during the period of 28 days. X‐ray photoelectron spectroscopy, atomic force microscopy, and O2 permeability were used to characterize the surface properties of EVOH films treated with PSII. The improved hydrophobic properties were closely related to the formation of fluorine‐containing functional groups such as CF, CF2, and CF3 on the modified surface. The percentage distribution of carbon functional groups supports the role of CF2 and CF3 groups in surface modification. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 2069–2075, 2004
Ion‐conducting polymer gels of polyacrylamide embedded with K2CO3
Authors: Song Wensheng , Wang Yuxin , Deng Huining 
Published: March 2004

AbstractA highly ionic conductive solid‐gel membrane based on polyacrylamide hydrogels with a K2CO3 additive was investigated. The polymer‐based gel was prepared by adding ionic species K2CO3 to a monomer solution followed by polymerization. After polymerization, the ionic species was embedded in the polymer‐based gel, where it remained. The ionic species behaved like a liquid electrolyte, whereas the polymer‐based solid‐gel membrane provided a smooth impenetrable surface that allowed for the exchange of ions. The gel membranes were obtained in the form of thin films of reasonable mechanical strength. Their ambient temperature conductivities were in the range 10−2 to 10−1 S/cm. The effect of K2CO3 concentration on the conductivity of the gels prepared was examined in the temperature range from 0 to 100°C. The microstructure and chemical composition of the gels studied were characterized by environmental scanning electron microscopy and FTIR, respectively. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 2076–2081, 2004
A phosphorus‐containing diamine for flame‐retardant, high‐functionality epoxy resins. I. Synthesis, reactivity, and thermal degradation properties
Authors: Liu Weichang , Varley Russell J. , Simon George P. 
Published: March 2004

AbstractA phosphorus‐containing amine, bis(4‐aminophenoxy)phenyl phosphine oxide (BAPP), suitable for curing epoxy resins with improved fire performance was synthesized and characterized with Fourier transform infrared spectroscopy and nuclear magnetic resonance. The reactivity of the amino group was evaluated by differential scanning calorimetry of the epoxy–amine mixture and by proton nuclear magnetic resonance of the amino unit. With BAPP as a curing agent, a range of high‐functionality, aerospace epoxy resins were cured, and the dynamic kinetic parameters calculated from Kissinger's and Ozawa's models were compared with those from the more widely used amines. The thermal degradation properties of the phosphorus‐containing epoxy resins were studied by thermogravimetric analysis, the degradation activation energy was calculated, and a multistep thermal degradation process was observed. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 2093–2100, 2004
Nanocomposites of poly(methyl methacrylate) and organically modified layered silicates by melt intercalation
Authors: Shen Zhiqi , Simon George P. , Cheng Yi‐Bing 
Published: March 2004

AbstractPolymer‐layered silicate nanocomposites of poly(methyl methacrylate) (PMMA) and an organically modified silicate [tetraallkyl ditallow ammonium bentonite (B34)] system prepared via melt intercalation were studied. The saturation ratio of PMMA to B34 was 25:75 (w/w), as determined by dynamic mechanical thermal analysis, differential scanning calorimetry, and X‐ray diffraction. The interaction between PMMA and B34 was detected by Fourier transform infrared spectrometry, which showed two new absorption bands of PMMA/B34 hybrids in comparison with unannealed physical mixtures of PMMA and B34. The degradation temperature of the PMMA/B34 hybrids was 26°C higher than that of neat PMMA according to thermogravimetric analysis, the thermal stability of the hybrids having been enhanced. The glass‐transition temperature of excess PMMA remaining outside the clay galleries was about 12–19°C higher than that of neat PMMA. A structural model of the hybrid was also presented. It involves some PMMA chains diffusing into the gallery of B34 and expanding it by 6.8 Å and some penetrating and interacting with the organic chains of the modified cations. Some of the PMMA chains partly contained inside the clay layers were entangled with those remaining outside when PMMA in excess of the saturation ratio was used. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 2101–2115, 2004
Concanavalin A attached poly(p‐chloromethylstyrene) beads for glycoenzyme separation
Authors: Bahar T. , Tuncel A. 
Published: March 2004

AbstractCrosslinked poly(p‐chloromethylstyrene) (PCMS) beads were produced by suspension polymerization. The beads had a nonporous but reasonably rough surface structure. Because of this property, a relatively high external surface area (i.e., 14.1 m2/g) was obtained with the proposed carrier. A biospecific ligand commonly used in the affinity chromatography of various glycoenzymes, concanavalin A (Con A), was covalently attached onto the bead surface by a direct chemical reaction. PCMS/Con A beads were then used for the separation of a model glycoenzyme, invertase, from its crude solution. The appropriate invertase adsorption and desorption conditions of the affinity system were investigated. The desorption of invertase from the carrier was achieved by the use of methyl‐α‐D‐mannopyranoside (MMP) as the counterligand. The effects of the MMP and salt concentrations and the temperature on the desorption behavior of invertase were investigated. The MMP concentration and temperature were found to be the dominant parameters controlling the desorption. Iterative experiments involving five reversible adsorption–desorption cycles were performed with the same particles to monitor the changes that occurred in the invertase adsorption–desorption capacities of Con A immobilized beads. The reversible adsorption–desorption stability was significantly improved by the crosslinking of Con A immobilized on the beads. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 2116–2124, 2004
Preparation and thermal analysis of cotton–clay nanocomposites
Authors: White Leslie A. 
Published: March 2004

AbstractNanocomposites were produced from cotton with montmorillonite clay used as the nanofiller material. Three exfoliation and intercalation methods with different solvents and clay pretreatment techniques were tested for the production of these organic–inorganic hybrids. The method that resulted in superior clay–cotton nanocomposites used a clay pretreatment with 4‐methylmorpholine‐N‐oxide as the cotton solvent. The nanocomposites showed significant improvements in the thermal properties in comparison with unbleached cotton and cotton processed under the conditions for nanocomposite preparation. The degradation temperature of the nanocomposites increased by 45°C, and the char yields for some compositions were twice those of unbleached cotton. The crystalline melt of the materials decreased by 15°C. Future research will include the development of textiles based on these cotton–clay materials and testing for flame‐retardant properties and product strength. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 2125–2131, 2004
Synthesis and material properties of syndiotactic polystyrene/organophilic clay nanocomposites
Authors: Ho Kim Mun , Park Cheon Il , Choi Won Mook , Lee Jin Woo , Lim Jae Gon , Park O Ok , Kim Jung Min 
Published: March 2004

AbstractSyndiotactic polystyrene (sPS)/organophilic clay nanocomposites were fabricated by direct‐melt intercalation method. To overcome the thermal instability of organophilic clay at high‐melt processing temperatures of sPS, an organophilic clay modified by alkyl phosphonium was adopted, which is known to be thermally stable. By using the newly synthesized clay, we could fabricate sPS intercalated nanocomposites. The microstructures of nanocomposites were confirmed by X‐ray diffraction (XRD) and transmission electron microscopy (TEM). The crystallization rate of nanocomposites investigated by differential scanning calorimetry (DSC) does not increase despite the presence of clay, which may be due to the physical hindrance of organic modifiers in the clay dispersion. Nanocomposites exhibited enhanced mechanical properties such as strength and stiffness relative to the virgin polymer. In addition, thermal stability was confirmed to be improved by thermogravimetric analysis (TGA). © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 2144–2150, 2004
13C‐NMR study of Dipteryx Alata Vogel starch
Authors: Tavares Maria Inês B. , Bathista André Luis B. S. , Silva Emerson O. , Costa Paula M. , Filho Nicolau P. , Nogueira José S. 
Published: March 2004

AbstractNatural starches obtained by fruit seeds have been a subject of studies because of their applications, as a consequence of their chemical properties. As it is known, the fruits depend on the geographic region. Because of this, several factors affect the seed starches nature, such as granules size, morphology, components, and composition. Thus, to better understand starch properties, it is necessary to investigate the chemical behavior of these factors. This work focused on the chemical components and molecular dynamic behavior of the Dipterxy Alata Vogel (cumbaru) starch, because this fruit is very popular and is used in abundance for people because they think that it is good for some kinds of diseases. The main chemical components and the molecular dynamics of starch from the Dipterxy Alata Vogel were studied by applying solid‐state 13C nuclear magnetic resonance spectroscopy (NMR). © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 2151–2154, 2004
Structural characterization of reactor blends of polypropylene and ethylene‐propylene rubber
Authors: Pires Márcia , Mauler Raquel S. , Liberman Susana A. 
Published: March 2004

AbstractBlends of isotactic polypropylene (PP), ethylene‐propylene rubber copolymer (EPR), and ethylene‐propylene crystalline copolymer (EPC) can be produced through in situ polymerization processes directly in the reactor and blends with different structure and composition can be obtained. In this work we studied the structure of five reactor‐made blends of PP, EPR, and EPC produced by a Ziegler‐Natta catalyst system. The composition of EPR was related to the ratio between ethylene and propylene used in the copolymerization step. The ethylene content in the EPR was in the range of 50–70 mol %. The crystallization behavior of PP and EPC in the blends was influenced by the presence of the rubber, and some specific interactions between the components could be established. By preparative temperature rising elution fractionation (P‐TREF) analysis, the isolation and characterization of crystalline EPC fractions were made. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 2155–2162, 2004
Free‐radical grafting of acrylic acid onto isotactic polypropylene using styrene as a comonomer in supercritical carbon dioxide
Authors: Dong Qingzhi , Liu Ying 
Published: March 2004

AbstractFree‐radical grafting of acrylic acid (AAc) onto isotactic polypropylene (iPP) using styrene (St) as a comonomer in supercritical carbon dioxide (SCCO2) medium was studied. The effects of temperature and pressure of reaction on functionalization degree (grafting degree of AAc) of the products were analyzed. The increase of reaction temperature increases the diffusion of monomers and radicals in the disperse reaction system of SCCO2. In addition, the increase of temperature accelerates the decomposition rate of 2,2′‐azobisisobutyronitrile (AIBN), thus promoting grafting reaction. It was also observed that functionalization degree of the products decreases with the increase of pressure of SCCO2 in the range of experiment. The effects of comonomer St on the functionalization degree of the products were investigated. The AAc graft degree of the resulting polymer was drastically higher in the present of St. It reached a maximum when the mass ratio of St and AAc was about 0.7 : 1. Because AAc is not sufficiently reactive toward iPP macroradicals, it would be helpful to use a second monomer that can react with them much faster than AAc. St preferentially reacts with the iPP macroradicals to form more stable styrene macroradicals, which then copolymerize with AAc to form branches. The highest functionalization degree was obtained when the AIBN was 0.75 wt %. When the initiator was used excessively, the functionalization degree decreased because of severe chain degradation of the iPP backbone. The morphologies of pure iPP and grafted iPP are different under the polarizing optical microscope. The diameter of the pure iPP spherulites is 20–38 μ and that of the grafted iPP spherulites is reduced with the increase of the functionalization degree of the products. This is proposed to be because the polar grafts formed during the reaction would have a tendency to associate in the hydrophobic PP environment. This might preserve some of the local crystalline order that existed during the reaction in the swollen iPP phase. It can be proven by a DSC cooling investigation that the crystallization temperature increased as the functionalization degree increased. This is proposed to be because the side‐chain of grafting polymer helps to bring about the heterogeneous nucleation in grafting polymer. Therefore, a large number of nuclei can emerge to a lesser supercooling degree. It can be also proven that the percent crystallization decreased as the functionalization degree increased, probably due to the grafted branches, which disrupted the regularity of the chain structure and increased the spacing between the chains. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 2203–2210, 2004
Rheological, electrical, and microwave properties of polymers with nanosized carbon particles
Authors: Kotsilkova R. , Nesheva D. , Nedkov I. , Krusteva E. , Stavrev S. 
Published: March 2004

AbstractThe rheology, dc‐conductivity, and microwave properties of acrylic, polyurethane, and epoxy composites containing 0–15 vol % of nanosized carbon particles have been investigated. Carbon nanoparticles (1–3 nm) are produced by a shock wave technology. Steady‐state shear and oscillatory flow tests are applied to investigate the rheological properties of dispersions; dc‐conductivity and MW absorption/reflection are investigated for solid composite films. Rheological characteristics are used for the evaluation of agglomeration processes of nanoparticles in dispersions, as controlled by volume fraction and processing technology. The percolation threshold is interpreted as a structural transition from a dispersed to an agglomerated state and it is found to depend significantly on the type of the matrix polymer. Above the percolation threshold, the presence of carbon nanoparticles produces a strong increase in the viscosity of dispersions as well as of the electrical conductivity and microwave properties of solid composites. A good correlation between the three characteristics is found for the systems in a wide range of carbon volume fractions. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 2220–2227, 2004