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  • 1
    Electronic Resource
    Electronic Resource
    Polymer–polymer interaction parameters for homopolymers and copolymers from light scattering and phase separation experiments in a common solvent (2001)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 115 (2001), S. 9536-9546 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The thermodynamic behavior of the quaternary system DMAc/PS/PAN/SAN and of all its solvent containing subsystems [DMAc: dimethylacetamide, PS: polystyrene, PAN: polyacrylonitrile, SAN: P(S–ran–AN)] was studied in terms of second virial coefficients and phase separation in the range of moderate polymer concentrations. The most remarkable finding consists in fundamental discrepancies between the Flory–Huggins parameters obtained for the interaction between the segments of polymer X and polymer Y either straightforwardly from the light scattering experiments (ranging from −0.88 to −0.14) and that resulting from the modeling of the measured phase diagrams (+0.01 to +0.33) or from solubility parameter theory (+0.03 to +1.92). The reasons for the disagreement even in the sign of the parameters are discussed in terms of A2XY, the second osmotic virial coefficients referring to the opening of intermolecular contacts between X and Y by the insertion of solvent and in terms of W2, the normalized excess Gibbs energy of contact formation between the two types of solute in the concentration region of pair interaction according to X–X+Y–Y→2X–Y. The pair interaction coefficient W2 results negative for PS/SAN, but positive for PAN/SAN and for PAN/PS. A theoretical explanation of this unexpected result is offered. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1412867
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  • 2
    Electronic Resource
    Electronic Resource
    Bedeutung der zellulären Selbstorganisation für die Tumorbiologie (1993)
    Springer
    Naturwissenschaften 80 (1993), S. 343-352 
    Details
    ISSN: 1432-1904
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Natural Sciences in General
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01138789
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  • 3
    Electronic Resource
    Electronic Resource
    Mikrosensorische Systeme in der zellbiologischen Grundlagenforschung und der medizinischen Diagnostik (1996)
    Springer
    Naturwissenschaften 83 (1996), S. 193-200 
    Details
    ISSN: 1432-1904
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Natural Sciences in General
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01143324
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  • 4
    Electronic Resource
    Electronic Resource
    Mikrosensorische Systeme in der zellbiologischen Grundlagenforschung und der medizinischen Diagnostik (1996)
    Springer
    Naturwissenschaften 83 (1996), S. 193-200 
    Details
    ISSN: 1432-1904
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Natural Sciences in General
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01143324
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  • 5
    Electronic Resource
    Electronic Resource
    Mikrosensor-gesteuerte Rückkopplungs- Bioaktuatoren auf Halbleiterbasis zur biophysikalischen Krebsbehandlung (1997)
    Springer
    Naturwissenschaften 84 (1997), S. 444-451 
    Details
    ISSN: 1432-1904
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Natural Sciences in General
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s001140050425
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  • 6
    Electronic Resource
    Electronic Resource
    Elektronen-Energieverlust-Spektroskopie (FELS) als Methode zur Lokalisierung von Antigenen und anderen Substanzen in Zellen und Geweben (1990)
    Springer
    Naturwissenschaften 77 (1990), S. 110-115 
    Details
    ISSN: 1432-1904
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Natural Sciences in General
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01134470
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  • 7
    Electronic Resource
    Electronic Resource
    Solidification behavior of the theta system 2-propanol/poly(n-butyl methacrylate) (1995)
    Springer
    Rheologica acta 34 (1995), S. 172-181 
    Details
    ISSN: 1435-1528
    Keywords: Thermoreversible gelation ; glass transition ; viscosity ; storage modulus ; loss modulus ; activation energies of flow ; entanglement molecular weights ; poly(n-butyl methacrylate) ; 2-propanol ; concentration and temperature influences
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Abstract Thermoreversible gelation of the system 2-propanol/poly (n-butyl methacrylate) — as detected by D'SC or dielectric experiments — does not manifest itself in a straightforward manner in the dynamic-mechanical properties. Its occurrence can, however, be seen in many ways: i) For constant composition of the system and a reference temperature lower than T gel, the storage modulus G′ is larger than the loss modulus G″ in the glass transition zone of the master curve and both vary in an almost parallel manner with the angular frequency ω over almost two decades (whereas this feature is normally found for other gelling systems within the rubber plateau or the flow region). ii) The entanglement molecular weight obtained from G″max is markedly less max than the entanglement molecular weight in the melt divided by ϕ2, the volume fraction of the polymer. iii) The temperature influences change from WLF like to Arrhenius-like behavior as T is lowered in the case of highly concentrated polymer solutions; analogous considerations hold true as ϕ2 is increased at constant T. iv) For sufficiently low temperatures, the activation energy of flow exhibits a maximum in the concentration range where the gelation is — according to DSC experiments — most pronounced. Like with ordinary non-gelling systems it is possible to construct master curves. On the basis of Graessley's theory identical dependencies are obtained for the variation of the entanglement parts of the stationary viscosity with shear rate and for the dependence of the entanglement part of the complex viscosity on the frequency ω of oscillation. Zero shear viscosity and limiting value of the complex viscosity for vanishing ω as a function of ϕ2 match smoothly and exhibit two points of inflection.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00398437
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  • 8
    Electronic Resource
    Electronic Resource
    Fully automated high performance capillary zone electrophoresis (1989)
    Springer
    Fresenius' Zeitschrift für analytische Chemie 333 (1989), S. 751-752 
    Details
    ISSN: 1618-2650
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00476608
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  • 9
    Electronic Resource
    Electronic Resource
    Interaction parameters in some ternary systems styrene/polystyrene/rubberDedicated to Professor Dr. Dr. h. c. Heinrich Hellmann on the occasion of his 65th birthday (1978)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 74 (1978), S. 113-122 
    Details
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Die isothermen Trübungskurven der Systeme Styrol/Polystyrol/Kautschuk (S/PS/R) zeigen für die drei unterschiedlichen Fälle (R =Polybutadien, Polypropylenoxid und EPDM), daß bei 25°C bereits bei einigen wenigen Prozenten Polybustyrol und Kautschuk ein Zerfall in zwei Phasen eintritt. Durch Trennung der Phasen (Zentrifuge) und Analyse von koexistenten Phasen konnten Konnoden und damit kritische Punkte festgelegt werden. Die Auswertung der Ergebnisse erfolgte auf der Grundlage der Theorie von Flory und Huggins mit Hilfe verschiedener von Scott für derartige Systeme angegebener Näherungen. Die dabei für 25°C resultierenden binären Wechselwirkungsparameter stimmen mit Literaturangaben - soweit vorhanden - gut überein. Mit Hilfe der erwähnten Näherungen wird untersucht, wie sich die vorliegenden ternären Systeme im experimentell schlecht zugänglichen Gebiet hoher Viskositäten bzw. Polymerkonzentrationen thermodynamisch verhalten sollten.
    Notes: For the three different cases (R=polybutadiene, polypropylene oxide and EPDM) the isothermal cloud point curves of the system styrene/polystyrene/rubber (S/PS/R) show that at 25°C a decomposition into two phases occurs already in the presence of a few percents of polystyrene and rubber. By separating the phases (centrifuge) and analysis of coexisting phases, tie lines and thus critical points could be fixed. Evaluation of the results was made on the basis of the Flory and Huggins theory by means of approximations given for such systems by Scott. The interaction parameters resulting for 25°C are well in agreement with literature data - as far as available. By means of the approximations mentioned, it was investigated how the presented ternary systems ought to behave thermodynamically in experimentally difficult areas of high viscosities or polymer concentrations respectively.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/apmc.1978.050740109
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  • 10
    Electronic Resource
    Electronic Resource
    Continuous polymer fractionation of polysaccharides using highly substituted trimethylsilylcellulose (1998)
    Weinheim : Wiley-Blackwell
    Macromolecular Chemistry and Physics 199 (1998), S. 1895-1900 
    Details
    ISSN: 1022-1352
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Trimethylsilylcellulose (TMSC) was prepared from commercial cellulose with a mixture of hexamethyldisilazane and chlorotrimethylsilane in the solvent system N,N-dimethylacetamide/lithium chloride. The soluble, highly silylated polymer (degree of substitution, DS 2.9) had a molar mass M̄w of 500 kg/mol and a molecular non-uniformity U = (M̄w/M̄n) - 1 of 2.9. In order to investigate the principal suitability of a continuous polymer fractionation for polysaccharides like cellulose derivatives and to obtain TMSC with different molecular weights and lower non-uniformity TMSC was fractionated by means of CPF (Continuous Polymer Fractionation), well-established in the field of synthetic polymers. The samples were fractionated using a mixed solvent, composed of toluene and dimethyl sulfoxide, and characterized by capillary viscometry, gel permeation chromatography (GPC), and GPC-light scattering coupling. The molar masses of the fractions range from 110 to 600 kg/mol and their U values vary between 0.9 and 1.9. The intrinsic viscosities of TMSC in tetrahydrofuran at 25°C and M̄w are related by [η] = K · Mwa, where K = 0.0089 mL/g and α = 0.82.
    Additional Material: 7 Ill.
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