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  • Chemistry  (14)
  • ASTROPHYSICS  (2)
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  • 1990-1994  (16)
  • 1991  (16)
  • 1
    Electronic Resource
    Electronic Resource
    Electron spin resonance studies of plasma-induced polystyrene radicals (1991)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 29 (1991), S. 1-7 
    Details
    ISSN: 0887-624X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Plasma-induced polystyrene radicals were first studied by electron spin resonance (ESR). The room temperature ESR spectrum was compared with those obtained by γ-irradiation, UV-irradiation, and mechanical fracture. It was found that even less than a few seconds of plasma-irradiation gave rise to a large amount of polystyrene radicals and the ESR spectrum consisted of two types of spectra, a triplet and a single broad line. The spectral feature of the triplet was nearly identical with that of γ-irradiated polystyrene. Thus, it was assigned to the structure of a cyclohexadienyl-type radical formed by a nearly random addition of a hydrogen atom to the aromatic ring. The single broad line, thought to be an outline of multicomponent spectrum, was assigned to an immobilized dangling-bond sites at the plasma-induced crosslinked portion of the polystyrene surface.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pola.1991.080290102
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  • 2
    Electronic Resource
    Electronic Resource
    Polymerization of α-methyleneindane: A cyclic analog of α-methylstyrene (1991)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 29 (1991), S. 1779-1787 
    Details
    ISSN: 0887-624X
    Keywords: α-methyleneindane ; tacticities ; monomer reactivity ratios ; exo-methylene cyclic monomers ; depropagation ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: α-Methyleniedane (MI), a cyclic analog of α-methylstyrene which does not undergo radical homopolymerization under standard conditions, was synthesized and subjected to radical, cationic, and anionic polymerizations. MI undergoes radical polymerization with α,α′-azobis(isobutyronitrile) in contrast to α-methylstyrene, owing to its reduced steric hindrance, though the polymerization is slow even in bulk. Cationic and anionic polymerization of MI with BF3OEt2 and n-butyllithium, respectively, proceed rapidly. The thermal degradation behavior of the polymer depends on the polymerization conditions. The anionic and radical polymers are heteortactic-rich. Reactivity ratios in bulk radical copolymerization on MI (M2) with methacrylate (MMA, M1) were determined at 60°C (r1 = 0.129 and r2 = 1.07). In order to clarify the copolymerization mechanism, radical copolymerization of MI with MMA was investigated in bulk at temperatures ranging from 50 to 80°C. The Mayo-Lewis equation has been found to be inadequate to describe the result due to depolymerization of MI sequences above 70°C.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pola.1991.080291210
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  • 3
    Electronic Resource
    Electronic Resource
    Elementary reaction and anionic polymerization of isopropenly t-butyl ketone (1991)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 29 (1991), S. 1001-1013 
    Details
    ISSN: 0887-624X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Isopropenyl t-butyl ketone (IPTBK) does not undergo radical homopolymerization and its anionic polymerization is a slow equilibrium process with a low ceiling temperature, which is due to its limited conjugation imposed by steric hindrance. Equimolar reactions of IPTBK with several anionic initiators were carried out, products isolated and identified by 1H-and 13C-NMR, and product distributions determined by GC. While n-butyllithium and phenyllithium preferentially produce allyl alcohols, Grignard reagents predominantly undergo β-addition to produce mono-adducts, and a significant amount of dimers. t-Butyllithium and t-butylmagnesium chloride provide the cleanest β-addition with minimal dimer formation and no carbonyl addition. However, Grignard reagent do not yield a polymer. The 1:1 reaction mixture of IPTBK with t-butyllithium is very stable at 0°C, providing a methyl-terminated mono-adduct quantitatively when quenched with methyl iodide after 29 h. Addition of a second IPTBK to the mono-adduct anion appears to be affected by the low ceiling temperature. Although t-butyllithium can efficiently reduce as well as add to di-t-butyl ketone, such reactions are minor in the presence of IPTBK. Anionic polymerization of IPTBK with t-butyllithium was carried out under several conditions. The 1:1 model reactions and the lack of acidic hydrogens in its structure suggest that anionic polymerization of IPTBK with t-butyllithium may be “living.” The molecular weight distribution of the polymers ranged from 1.1 to 1.6 with the number-average molecular weight varying from 2,800 to 233,500. Group transfer polymerization of IPTBK produced only a six-membered lactone.
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pola.1991.080290707
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  • 4
    Electronic Resource
    Electronic Resource
    Mechanistic study on photocuring of a methacrylates copolymer by benzophenones (1991)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 42 (1991), S. 409-415 
    Details
    ISSN: 0021-8995
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: The types of photochemical reactions that will occur in the photosensitive resin for optical devices, poly(methyl methacrylate-co-crotyl methacrylate) (PMMA-CMA) doped with meta-benzoylbenzophenone (BBP), were investigated. Oxetane formation, hydrogen abstraction followed by radical coupling, and pinacol formation were found to occur. The quantum yield for disappearance of benzophenone (BP) in the PMMA-CMA film was estimated as 0.68. The pendant crotyl group seems to be a major photoreaction site.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/app.1991.070420213
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  • 5
    Electronic Resource
    Electronic Resource
    Copolymerization of methacrylic acid alkali metal salts and polyether-containing monomers in solid polymer electrolytes (1991)
    New York, NY : Wiley-Blackwell
    Polymers for Advanced Technologies 2 (1991), S. 97-101 
    Details
    ISSN: 1042-7147
    Keywords: Copolymerization ; Salt monomer ; Ionic conductivity ; Polyether macromonomer ; Cation radius ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Copolymerization of methacrylic acid alkali metal salts (MAAM; M = Li, Na, K, Rb or Cs) and oligo(oxyethylene) methacrylate (MEO) was carried out in bulk or in poly(oligo(oxyethylene) methacrylate) (PMEO) at 60°C. The copolymers of MAAM and MEO which were obtained by bulk polymerization showed a cation conductivity of around 1 × 10-7 S/cm at room temperature. On the other hand, the copolymers obtained by radical polymerization in PMEO, showed a higher cation conductivity (10-6-10-5 S/cm). Furthermore, higher cation conductivity was observed for the copolymer systems containing alkali metal cations with a larger ion radius. This tendency was explained by the strength of the bond between alkali metal cation and ether oxygens. The degree of dissociation had little effect on this difference in the conductivity. The effective dissociation of methacrylic salts was enhanced in the copolymer compared to the homopolymer because of the suppression of the adjacent dissociative carboxylic acid groups. Arrhenius plots for ionic conductivity show the migration of ions along with the segmental motion of the polymer matrix.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pat.1991.220020208
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  • 6
    Electronic Resource
    Electronic Resource
    Polyelectrolyte-like behavior of polyethylene oxide/LiClO4 mixture in chloroform or chloroform/dimethylformamide mixed solvent (1991)
    New York, NY : Wiley-Blackwell
    Polymers for Advanced Technologies 2 (1991), S. 213-217 
    Details
    ISSN: 1042-7147
    Keywords: Polyethylene oxide ; Lithium perchlorate ; Chloroform ; Viscosity ; Electrostatic repulsion ; Ion-dipole interaction ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Lithium perchlorate (LiClO4) was dissolved in dehydrated chloroform with polyethylene oxides (PEO) having different molecular weights. The mixing ratio of ether oxygen unit (—O—) of PEO to cation (Li+) was set to 20:1. The solution viscosity of the PEO/LiClO4 mixtures was measured using an Ubbelohde viscometer at 30.0°C. The concentration dependence of the reduced viscosity was analyzed by diluting the initial PEO/LiClO4 mixed solution with pure chloroform to keep the ratio of —O—to Li+ constant. The increase in the reduced viscosity for a dilute solution was found in every mixture system, but not in the PEO solution without salt. Similar experiments were also carried out in chloroform/dimethylformamide (DMF) mixed solvent (4:1 by volume). These results were analyzed using the Fuoss equation, which was applied for the analysis of a polyelectrolyte aqueous solution. Linear relations are depicted in the Fuoss plots, suggesting that the PEO/LiClO4 mixture shows polyelectrolyte-like behavior in chloroform or in chloroform/DMF mixed solvent. This is attributed to the intramolecular electrostatic repulsion of lithium cations which are trapped by the PEO chains through ion-dipole interaction.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pat.1991.220020501
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  • 7
    Electronic Resource
    Electronic Resource
    The mass spectrum of mercury/cesium complex clusters (Hg)n Cs+ ranging up to m/z = 118 000 (1991)
    New York, NY : Wiley-Blackwell
    Rapid Communications in Mass Spectrometry 5 (1991), S. 437-440 
    Details
    ISSN: 0951-4198
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Notes: The mass spectrum of mercury/cesium complex clusters (Hg)nCs+ is observed up to m/z=118 000 (n = 590). Singly charged clusters are produced by Cs+ ion bombardment. The presence of an alkali metal in the ionization process yields cluster ions of the form (Hg)nX+. The clusters are analysed using the grand-scale mass spectrometer, GEMMY, at Osaka University. The mass resolution of the instrument is high enough to resolve each cluster up to m/z=70 000. From the pattern of cluster distribution, the structrues of the large clusters can be studied. The number of Hg groups in metastable decay increases with the cluster size n. The ion intensities of the mercury/cesium clusters are much stronger than that from CsI (used for mass calibration). The mass spectrum of the clusters can therefore easily be utilized for direct mass calibration up to m/z=70 000.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/rcm.1290051003
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  • 8
    Electronic Resource
    Electronic Resource
    Optimization of a high speed countercurrent chromatograph for analytical separations (1991)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 14 (1991), S. 306-311 
    Details
    ISSN: 0935-6304
    Keywords: High speed countercurrent chromatography ; Two-phase solvent system ; Column diameter ; Optimization ; Indole auxins ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The analytical capability of the high speed countercurrent chromatograph model 4000 (HSCCC-4000) has been improved by optimizing the dimensions of the multilayer coiled column. Using a two-phase solvent system of n-hexane - ethyl acetate - methanol - water (1:1:1:1) and a set of indole auxins as test samples, a series of studies was conducted to evaluate performance of coiled columns with i.d.s ranging from 0.1 to 0.55 mm. The studies on the stationary phase retention indicated that multilayer coils of 0.55 mm and 0.30 mm i.d. provide satisfactory retention of the stationary phase while the 0.10 mm i.d. column fails to yield reproducible retention. The best partition efficiencies were obtained from the 0.30 mm i.d. multilayer coil with a 6 ml capacity which produced theoretical plate numbers ranging from 5500 to 10500 with a resolution factor of 2.30. The feasibility of interfacing the HSCCC-4000 with a mass spectrometer is briefly discussed.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jhrc.1240140503
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  • 9
    Electronic Resource
    Electronic Resource
    Interaction of poly(sodium vinyl sulfonate) and its surface graft with antithrombin III (1991)
    Hoboken, NJ : Wiley-Blackwell
    Journal of Biomedical Materials Research 25 (1991), S. 99-115 
    Details
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: Poly(sodium vinyl sulfonate) (PVS) was found to be 1/14 times as active as heparin in inducing the conformational change and activation of antithrombin III. The conformational change of antithrombin III was investigated in terms of the intrinsic fluorescence of tryptophan residue, the extrinsic fluorescence using 1,6-diphenyl-1,3,5-hexatriene as fluorescent probe, and Fourier-transform infrared spectroscopy. It was evident in the experiment using 2,4,6-trinitrobenzene sulfonate that PVS elicited the activity of antithrombin III by interacting with amino groups of the protein as does heparin.Sodium vinyl sulfonate was graft-polymerized onto polyetherurethane (PEU) film that was treated with glow discharge in advance. PVS-grafted PEU film adsorbed antithrombin III easily and, like ungrafted PVS, induced conformational change and activation of antithrombin III. However, the mechanism of interaction of the PVS graft with antithrombin III did not seem to be completely the same as that of ungrafted PVS in solution.
    Additional Material: 14 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jbm.820250108
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  • 10
    Electronic Resource
    Electronic Resource
    Synthesis and nonthrombogenicity of polyetherurethaneurea film grafted with poly(sodium vinyl sulfonate) (1991)
    Hoboken, NJ : Wiley-Blackwell
    Journal of Biomedical Materials Research 25 (1991), S. 1347-1361 
    Details
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: Synthesis of nonthrombogenic materials without using biologically active substances was explored. Poly(sodium vinyl sulfonate) is a water-soluble synthetic polymer and activates antithrombin III to exert nonthrombogenicity that was dependent on the molecular weight. Polyetherurethaneurea film was plasmatreated and graft-polymerized with sodium vinyl sulfonate. The graft film showed excellent in vitro and ex vivo nonthrombogenicity by suppressing interactions with plasma proteins and platelets as well as by inactivating bloodclotting factors.
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jbm.820251104
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