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  • 1
    Electronic Resource
    Electronic Resource
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 36 (1998), S. 737-748 
    ISSN: 0887-624X
    Keywords: inverse microemulsion polymerization ; MADQUAT ; nucleation ; photopolymerization ; molecular weights ; flocculants ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The polymerization of inverse microemulsions of 2-methacryloyl oxyethyl trimethyl ammonium chloride stabilized by a blend of nonionic emulsifiers (a sorbitan sesquioleate and a sorbitan monooleate) and initiated by UV light in the presence of Azobis(isobutyronitrile) (AIBN) was investigated. The effect of initiator concentration, light intensity, emulsifier concentration, and dispersed phase weight fraction on the polymerization rate (Rp), number of polymer particles (Np), and polymer molecular weight (Mw) was studied. The application of this process to tubular reactors is discussed. © 1998 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 36: 737-748, 1998
    Additional Material: 15 Ill.
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  • 2
    ISSN: 0887-624X
    Keywords: ether ketones ; synthesis ; NMR ; thermal properties ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Linear polyaryl(ether ketones) containing tert-butyl pendent groups were prepared from aromatic hydrocarbons and aromatic diacid chlorides, both classes of monomers containing tert-butyl pendent groups. The polymers were prepared in high yield and high molecular weight by low-temperature precipitation polycondensation in 1,2-dichloroethane. The presence of meta-oriented moieties and bulky pendent groups played a beneficial role with regard to solubility, while the thermal transitions and thermal resistance were not greatly impaired relative to conventional all para-oriented polyaryl(ether-ketones). The current polyaryl(ether-ketones) showed glass transition temperatures in the range 170-240°C and decomposition temperatures, as measured by TGA, of about 500°C. © 1998 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 36: 1251-1256, 1998
    Additional Material: 3 Ill.
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  • 3
    ISSN: 1434-1948
    Keywords: Rhodium ; N ligands ; Carbonyl complexes ; Methoxycarbonyl ; Dinuclear complexes ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The reaction of 1,4,7-trimethyl-1,4,7-triazacyclononane (Cn*) with [{(CO)2Rh(μ-Cl)}2] in methanol at 0°C, followed by the addition of NH4PF6, results in the formation of the mononuclear carbonyl complex [Cn*Rh(μ-CO)2]PF6 ([1]PF6), the dinuclear carbonyl complex [Cn*Rh(μ-CO)3RhCn*](PF6)2 {[2](PF6)2} and the dinuclear methoxycarbonyl complex [Cn*Rh(C(O)OMe)(μ-CO)2RhCn*]PF6 ([3]PF6). The reaction of [2](PF6)2 with NaOMe results in formation of [3]PF6 by the attack of the methoxide at a bridging carbonyl. Treatment of [3]PF6 with NH4PF6 regenerates [2](PF6)2, thus showing that the methoxylation of [2](PF6)2 is reversible. The structures of [1]PF6, [2](PF6)2 and [3]PF6 have been determined by single-crystal X-ray diffraction. For [3]PF6 an unprecendented facile, reversible, migration of the C(O)OMe ligand between the two rhodium centres of the Rh(μ-CO)2Rh core is observed.
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  • 4
    Electronic Resource
    Electronic Resource
    Hoboken, NJ : Wiley-Blackwell
    Journal of Biomedical Materials Research 40 (1998), S. 520-529 
    ISSN: 0021-9304
    Keywords: 3D carbon/carbon composite ; collagen/apatite composite ; coating ; grafting ; phosphorylation ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: A three-dimensional carbon/carbon composite (3D C/C) was studied as potential bone-repairing material; its major mechanical properties were found to be closer to those of human bone than other common bone-repairing materials available. In vitro calcification tests revealed that as-received 3D C/C is almost bioinert in simulated body fluid (SBF) over an immersion period of 4 weeks. To improve the bioactivity of 3D C/C, surface modification was accomplished through two practical routes: (1) grafting with polyethylene glycol (PEG) and (2) phosphorylation and precalcification. After grafting with α, ω di(aminopropyl) polyethylene glycol 800 (NH2-PEG-NH2), a continuous layer of calcium phosphate was formed on the surface of 3D C/C in SBF after 4 weeks. Phosphorylated 3D C/C samples have the ability to induce apatite precipitation after precalcification in a saturated Ca(OH)2 solution for 1 week. To speed up the coating process, a calcification solution with collagen was developed in which a collagen/apatite coating layer can be formed on 3D C/C in 9 h in ambient conditions. © 1998 John Wiley & Sons, Inc. J Biomed Mater Res, 40, 520-529, 1998.
    Additional Material: 10 Ill.
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  • 5
    Electronic Resource
    Electronic Resource
    Hoboken, NJ : Wiley-Blackwell
    Journal of Biomedical Materials Research 41 (1998), S. 227-236 
    ISSN: 0021-9304
    Keywords: commercially pure titanium ; Ti6Al4V ; calcium phosphate ; chemical treatment ; surface modification ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: A two-step chemical treatment has been developed in our group to prepare commercially pure titanium (cpTi) surfaces that will allow calcium phosphate (Ca-P) precipitation during immersion in a supersaturated calcification solution (SCS) with ion concentrations of [Ca2+] = 3.10 mM and [HPO42-] = 1.86 mM. It was observed that a precalcification (Pre-Ca) procedure prior to immersion could significantly accelerate the Ca-P deposition process. In this work, the bioactivity of chemically treated cpTi and Ti6Al4V was further verified by applying commercially available Hanks' balanced salt solution (HBSS), an SCS with very low ion concentrations of [Ca2+] = 1.26 mM and [HPO42-] = 0.779 mM, as the immersion solution. It was found that a uniform and very dense apatite coating containing magnesium impurities was formed if the Pre-Ca procedure was performed before immersion, as compared with the loose Ca-P layer obtained from the abovementioned high concentration of SCS. The formation of a microporous titanium dioxide thin surface layer on cpTi or Ti6Al4V by the two-step chemical treatment could be the main reason for the induction of apatite nucleation and growth from HBSS. Variations of pH values, Ca and P concentrations, and immersion time in HBSS were investigated to reveal the detailed process of Ca-P deposition. The described treatments provide a simple chemical method to prepare Ca-P coatings on both cpTi and Ti6Al4V. © 1998 John Wiley & Sons, Inc. J Biomed Mater Res, 41, 227-236, 1998.
    Additional Material: 10 Ill.
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  • 6
    ISSN: 0935-6304
    Keywords: high temperature gas chromatography ; flavonoids ; propolis ; high molecular weight compounds ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---The underivatized acetone and hexane fractions from propolis samples (predominant flora Citrus spp. and Vernonia polyanthes) were analyzed by HT-HRGC (high temperature high resolution gas chromatography) and HT-HRGC coupled to mass spectrometry (HT-HRGC-MS). Several compounds, including flavonoid aglycones, phenolic acids, and high molecular weight compounds were characterized in crude extracts by HT-HRGC-MS. HT-HRGC and HT-HRGC-MS were shown to be quick and informative tools for rapid analysis of crude extracts without need for prior derivatization and purification.
    Additional Material: 4 Ill.
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  • 7
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 21 (1998), S. 411-413 
    ISSN: 0935-6304
    Keywords: Modulator ; GC x GC ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 3 Ill.
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  • 8
    ISSN: 0935-6304
    Keywords: Bornane congeners ; toxaphene compounds ; heart-cut multidimensional gas chromatography ; enantioselectivity ; chiral GC separation ; biological samples ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---The enantiomeric ratios of the chlorinated bornanes, 2-exo, 5,5,9,9,10, 10-heptachlorobornane (B[20030]-(022)), 2-endo,3-exo,5-endo,6-exo,8, 8,10,10-octachlorobornane (B[12012]-(202), Parlar No. 26), 2-exo,3-endo,6-endo,8,9,10,10-heptachlorobornane (B[21001]-(112)), 2,2,5,5,9,9, 10,10-octachlorobornane (B[30030]-(022), Parlar No. 38), 2-endo,3-exo,5-endo6-exo,8,8,9,10,10-nonachlorobornane (B[12012]-(212), Parlar No. 50), and 2,2,5,5,8,9,9,10,10-nonachlorobornane (B[30030]-(122), Parlar No. 62) were determined in a hake liver (Merluccius merluccius) and in two whitebeaked dolphin blubber (Lagenorynchus albirostris) samples. The analysis was performed by heart-cut multidimensional gas chromatography using an electron capture detector (ECD). Ultra 2 (5%-phenyl-95%-methylsilicone) was used as stationary phase in the first column and enantioselectivity was obtained in the second column with a phase consisting of a mixture of OV-1701 and heptakis(2,3,6-O-tert- butyldimethylsilyl)-β-cyclodextrin (10 : 1). All reference standards were also tested on the enantioselective column alone. The comparison of the two systems showed that deviations of ±0.12 from the racemic enantiomer ratio can be observed for the single column due to co-eluting impurities which are present in the reference standards. In most of the heart-cut chromatograms of the biota samples about 15 peaks could be found, showing the importance of a multidimensional separation system for an interference-free quantification by ECD. In all biological samples a significant deviation from the racemic enantiomer ratio was found for B[30030]-(022) (Parlar No. 38) and for B[30030]-(122) (Parlar No. 62). This indicates that an enantioselective disposition of the congeners occurs. In addition, considerations are presented concerning the relationship between congener structure and enantiomeric disposition.
    Additional Material: 4 Ill.
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  • 9
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Macromolecular Theory and Simulations 7 (1998), S. 41-48 
    ISSN: 1022-1344
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The reasons for the reactivity increase toward acyl chlorides caused in aromatic amines by silylation are studied by quantum semiempirical and ab initio methods. Silylated amino groups adopt an sp2 planar geometry, in contrast to that observed in the unsilylated series, where a partially pyramidal structure intermediate between sp3 and sp2 geometry was obtained. Silylation also causes a strong increase of electronic density on the amine nitrogen and an increase of the Highest Occupied Molecular Orbital (HOMO) energy, both effects favoring the higher reactivity of these silylated amines. In addition to that, silylation produces a decrease of the activation energy in the reaction with an acyl chloride, relative to the unsilylated amines, thus increasing reaction rate.
    Additional Material: 4 Ill.
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  • 10
    Electronic Resource
    Electronic Resource
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 36 (1998), S. 395-402 
    ISSN: 0887-6266
    Keywords: syndiotactic polypropylene ; form-IV ; form II ; kink bands ; Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The packing of the chains in (T6G2T2G2)n conformation of the form IV of s-PP is revisited on the basis of packing energy and structure factor calculations. According to this analysis, an alternative mode of packing has been suggested. A monoclinic structural model, with the unit cell centered on the C face, is obtained, after small changes of the atomic coordinates in the triclinic structural model as proposed by Chatani et al. The monoclinic model presents a lower packing energy than the triclinic model and a good agreement between the calculated and observed structure factors. The triclinic structural model implies that all the chains are rotated by the same amount around the chain axis with respect to the monoclinic structural model. Since clockwise and counter clockwise rotations are equivalent, the monoclinic structural model may be taken as descriptive of the order in the long range, for the form IV of s-PP, or in other terms, descriptive of an average structure (space group C2, unit cell constants equal to am = 14.17 Å, bm = 5.72 Å, cm = 11.6 Å, and βm = 108.8°). The triclinic structural model for this polymorph, instead (space group P1, unit cell constants equal to at = 5.72 Å, bt = 7.64 Å, ct = 11.60 Å, αt = 73.1°, βt = 88.8°, γt = 112.0°) is probably more properly descriptive of local situation of order (the symmetry, locally, is broken). Analogies between the monoclinic limit ordered structural model for the form IV and the orthorhombic limit ordered structural model for the form II (with chains in the more stable (TTGG)n conformation) of s-PP are also provided. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36: 395-402, 1998
    Additional Material: 5 Ill.
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