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  • 1
    Electronic Resource
    Electronic Resource
    Mixtures of charged colloids and nonadsorbing flexible polyelectrolytes: An integral equation study (2000)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 113 (2000), S. 9849-9862 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: We study the equilibrium and structural properties of mixtures of like-charged colloids and nonadsorbing flexible polyelectrolytes using liquid state integral equations. The polymer chains in the semidilute regime are treated within the polymer reference interaction site model. The monomers and the colloids interact via screened Coulomb potentials (Debye–Hückel level). The electrostatic interactions between the different macromolecules inside the solution are responsible for complex local structures and rich phase diagrams, which depend on the charges and on the Debye screening length. The pair correlations between colloids are interpreted in terms of the effective, polymer-averaged, colloid–colloid pair potential. A first-order picture indicates that the Coulombic depletion attraction due to the osmotic pressure of the semidilute network against the colloidal particles dominates the direct repulsion at high enough monomer concentration and induces the liquid–liquid phase separation. Higher-order effects involving correlations inside the polyelectrolyte system alter this simple picture. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1322083
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  • 2
    Electronic Resource
    Electronic Resource
    New Methyl Dehydroabietate Derivatives: Synthesis and Structural Characterization (1998)
    Springer
    Monatshefte für Chemie 129 (1998), S. 1183-1197 
    Details
    ISSN: 1434-4475
    Keywords: Keywords. Chemical transformation; Methyl dehydroabietate; Chalcones; Pyrazoles; Pyrazolines.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Zusammenfassung.  Die Synthese einiger neuer Derivate des Dehydroabietinsäuremethylesters vom Typ der Chalkone und Pyrazole wird beschrieben. Alle Verbindungen wurden mit Hilfe von NMR- und MS-Techniken charakterisiert. Um die Ergebnisse dieser Techniken zu sichern, wurden Röntgen-Einkristallstrukturanalysen des 12-Acetyldehydroabietinsäuremethylesters und des entsprechenden (12-(4-Methoxycinnamoyl)-Derivates durchgeführt. Mittels molekülmechanischer Berechnungen wurde der Einfluà der Raumerfüllung des Substituenten in Position 12 auf die Konformation der Isopropylgruppe in diesen Derivaten studiert. Energiebarrieren von 52.3 und 53.6 kJ/mol für diese beiden Verbindungen weisen darauf hin, daà die freie Rotation der Isopropylgruppe in beiden Fällen sterisch gehindert ist.
    Notes: Summary.  The synthesis of some new chalcone and pyrazole type derivatives of methyl dehydroabietate is described. All compounds were exhaustively characterized using NMR and MS techniques. In order to confirm the information obtained by those techniques, the X-ray single crystal structures of methyl 12-acetyldehydroabietate and methyl 12-(4-methoxycinnamoyl)-dehydroabietate were determined. Molecular mechanics calculations were performed in order to evaluate the steric influence of the bulk of the C-12 substituent on the conformational preference of the isopropyl group in these derivatives. The energy barriers of 52.3 and 53.6 kJ/mol found for the two compounds indicated that the C-12 substituent hinders the free rotation of the isopropyl group in both cases.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/PL00010130
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  • 3
    Electronic Resource
    Electronic Resource
    Structural Studies of MCM-48 Derivatized with (1,1′-Ferrocenediyl)dimethylsilane (2000)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 2000 (2000), S. 97-102 
    Details
    ISSN: 1434-1948
    Keywords: Mesoporous materials ; MCM-48 ; Immobilization ; (1,1′-Ferrocenediyl)dimethylsilane ; 13C and 29Si solid-state NMR ; Sandwich-complexes ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The walls of the cubic mesoporous silicate MCM-48 have been grafted with ferrocenyl end groups by a ring-opening reaction of the ansa-bridged ferrocene [Fe{(η-C5H4)2SiMe2}], carried out in a pentane solution at room temperature. The orange product has been characterized by elemental analysis, powder X-ray diffraction, 13C and 29Si solid-state NMR, N2 adsorption measurements, and Fe K-edge EXAFS. A high loading has been obtained (8.18 mass % Fe) and, as a result of the inclusion of the organometallic moiety, the N2 adsorption isotherm exhibits a lower uptake. Direct structural evidence for the surface attachment of both single ferrocenyl and short chain oligo(ferrocenyl) fragments has been obtained.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
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    Paper (German National Licenses)
  • 4
    Electronic Resource
    Electronic Resource
    Structural Studies of MCM-48 Derivatized with(1,1′-Ferrocenediyl)dimethylsilane (2000)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 2000 (2000), S. 576-576 
    Details
    ISSN: 1434-1948
    Keywords: Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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    Paper (German National Licenses)
  • 5
    Electronic Resource
    Electronic Resource
    Structural Studies and Catalytic Activity of MCM-41 and MCM-48 Modified With the Titanocenophane [SiMe2(η5-C5H4)2]TiCl2 (2000)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 2000 (2000), S. 551-557 
    Details
    ISSN: 1434-1948
    Keywords: Mesoporous materials ; MCM-41 ; MCM-48 ; Immobilisation ; Solid-state NMR ; Heterogeneous catalysis ; Titanium ; Titanocenes ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Titanium(IV)-grafted mesoporous silicas have been prepared by diffusion of an excess of the ansa-bridged titanocene [SiMe2(η5-C5H4)2]TiCl2 into the channels of hexagonal MCM-41 and cubic MCM-48 in dichloromethane or tetrahydrofuran at room temperature. The choice of solvent determines the course of the reaction and hence the activity of the resulting materials as catalysts in the catalytic epoxidation of cyclooctene with tert-butylhydroperoxide. Magic-angle spinning (MAS) NMR (13C, 29Si) spectroscopy was used to characterise the local environment of the surface-bound titanium active sites. When dichloromethane is used, the dominant species anchored to the surface are isolated ansa-bridged titanocene fragments. When THF is used, the [SiMe2(η5-C5H4)2] unit is lost with the concomitant formation of surface-bound TiIV species coordinated by THF molecules. These materials showed the best catalytic performance per Ti atom for the conversion of cyclooctene. All materials were further characterised by means of elemental analysis, powder X-ray diffraction (XRD), N2 adsorption and FTIR spectroscopy.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
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    Paper (German National Licenses)
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