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  • 1
    Electronic Resource
    Electronic Resource
    Sedimentation von gelösten Makromolekülen in der Nähe des kritische Punktes im Schwerefeld der Erde (1974)
    Springer
    Colloid & polymer science 252 (1974), S. 345-345 
    Details
    ISSN: 1435-1536
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01551192
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  • 2
    Electronic Resource
    Electronic Resource
    Zur wechselseitigen Löslichkeitsbeeinflussung von Polymeren mit verschiedenen Molekulargewichten, 2. Mitt.: Mischlösungsmittel mit präferentieller Fällungsmitteladsorption durch das Polymere (1970)
    Springer
    Monatshefte für Chemie 101 (1970), S. 57-64 
    Details
    ISSN: 1434-4475
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Abstract The cloud-point curve for a solution containing equal amounts of two polystyrene samples of different molecular weight has been compared with the cloud-point curves of the components for the system CHCl3/acetone/polystyrene. In the mixed solvent under investigation the non-solvent is preferentially adsorbed into the interior of the polymer coil. As far as the mutual influence of the polymers on the solubility is concerned the system behaves like the single solvent system cyclohexane-polystyrene. The temperature range covered by the cloud-point curve on the other hand strongly increases with the non-uniformity of the polymer. The variation of the type of the cloud-point curve as compared with single solvents (decrease in the precipitation temperature with increasing polymer concentration over the entire range in the case of the polymolecular samples studied) is explained by the variation of the “effective solvent power” with the polymer concentration. For the sample with a “most probable” molecular weight distribution the critical point coincides with the inflection point of the cloud-point curve. The evaluation of physically significant pair interaction constants from the measured critical concentrations on the basis of theFlory-Huggins theory is not possible; this finding is explained by the fact, that also a structure effect has to be considered.
    Notes: Zusammenfassung Für das System CHCl3/Aceton/Polystyrol wurde die Trübungskurve einer Mischung aus gleichen Gewichtsteilen zweier Polystyrole mit verschiedenen Molekulargewichten mit den Trübungskurven der Komponenten verglichen. Das untersuchte Mischlösungsmittel, aus dem die Fällungsmittelkomponente bevorzugt ins Polymerknäuel aufgenommen wird, zeigt eine ähnliche wechselseitige Löslichkeitsbeeinflussung der Polymeren wie das Cyclohexan — Polystyrolsystem (Einkomponentenlösungsmittel). Der Temperaturbereich, über den sich die Trübungskurve erstreckt, nimmt mit steigender Uneinheitlichkeit der Polymeren stark zu. Die Änderung im Typ der Trübungskurve, verglichen mit Einkomponentenlösungsmitteln (Abnahme der Trübungstemperatur für die untersuchten polymolekularen Proben mit steigender Polymerkonzentration über den gesamten Bereich), wird zurückgeführt auf die Änderung der “effektiven Lösungsmittelgüte” mit der Polymerkonzentration. Für die untersuchte Probe mit “wahrscheinlichster” Molekulargewichtsverteilung fällt der kritische Punkt mit dem Wendepunkt der Trübungskurve zusammen. Aus den gemessenen kritischen Konzentrationen können auf der Grundlage derFlory-Huggins-Theorie keine physikalisch sinnvollen Wechselwirkungsparameter berechnet werden; dieser Befund wird auf die Nichtberücksichtigung des Struktureffekts durch die obige Theorie zurückgeführt.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00907525
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  • 3
    Electronic Resource
    Electronic Resource
    Röntgenkleinwinkeluntersuchungen an Lösungen eines Polystyrolpräparates mit enger Molekulargewichtsverteilung (1970)
    Springer
    Monatshefte für Chemie 101 (1970), S. 1462-1470 
    Details
    ISSN: 1434-4475
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Abstract Investigations were made of the scattering behaviour of polystyrene in the thermodynamically “bad” solvent cyclohexane between precipitation-temperature andϑ-temperature. At theϑ-point and close to it the behaviour of a statistically coiled chain molecule is found. Belowϑ-temperature an aggregation is beginning. Just above precipitation-temperature the molecular weight corresponds to an entanglement of two chain molecules. Appearance of compact polymer coils could not be noted at this temperature. The influence of the chain crosssection upon the scattering curve is considerable as the crosssection is not much smaller than the persistence length. Nevertheless, the persistence length (a=12.2 Å) may be determined from the transition point between the ranges roughly proportional to 1/(2ϑ)2 and 1/(2ϑ) as the break within the transition range is very distinct on account of the great number of persistence lengths per molecule.
    Notes: Zusammenfassung Es wurde das Streuverhalten von Polystyrol im thermodynamisch „schlechten” Lösungsmittel Cyclohexan zwischen Entmischungstemperatur undϑ-Temperatur untersucht. Beim ϑ-Punkt und nahe dabei liegt das Verhalten eines statistisch verknäuelten Fadenmoleküls vor. Unterhalb derϑ-Temperatur beginnt eine Aggregation. Knapp oberhalb der Entmischungstemperatur entspricht das Molekulargewicht etwa einer Verhängung zweier Fadenmoleküle. Ein Auftreten von kompakten Polymerknäueln ist bei dieser Temperatur nicht festzustellen. Der Einfluß des Fadenquerschnitts auf die Streukurve ist beträchtlich, da der Querschnitt nicht viel kleiner als die Persistenzlänge ist. Trotzdem läßt sich die Persistenzlänge (a=12,2 Å) aus dem Übergangspunkt zwischen den etwa 1/(2ϑ)2 und 1/(2ϑ) proportionalen Bereichen bestimmen, da der Knick im Übergangsbereich infolge der großen Anzahl von Persistenzlängen pro Molekül sehr ausgeprägt ist.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00911412
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  • 4
    Electronic Resource
    Electronic Resource
    Abbau von polystyrol in cyclohexanlösung bei kleiner schergeschwindigkeit (1973)
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 164 (1973), S. 353-355 
    Details
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Additional Material: 1 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/macp.1973.021640133
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  • 5
    Electronic Resource
    Electronic Resource
    Sedimentation of dissolved macromolecules in the terrestrial gravitational field near the critical locus (1972)
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 161 (1972), S. 277-284 
    Details
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Die vorliegende Arbeit zeigt sowohl theoretisch als auch experimentell, daß das Schwerefeld der Erde unter annähernd kritischen Bedingungen ausgeprägte Veränderungen in der Gleichgewichtskonzentration von gelösten Makromolekülen mit der Höhe hervorruft.So wurde für das System Polystyrol/Cyclohexan beobachtet, daß die Gleichgewichtskonzentration unter derartigen Bedingungen am Boden eines Gefäßes etwa das Dreifache beträgt wie in 10 cm Höhe. Im Falle polymolekularer Proben ist die Sedimentation von einer entsprechenden Fraktionierung begleitet.
    Notes: The present paper demonstrates theoretically as well as experimentally, that the gravitational field of the earth produces very pronounced changes in the equilibrium concentration of dissolved macromolecules with height, under near critical conditions.Thus it could be observed for the system polystyrene/cyclohexane that the equilibrium concentration at the bottom of a tube is approximately three times that at a height of 10 cm, under such conditions. In the case of polymolecular samples the sedimentation is associated with a corresponding fractionation.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/macp.1972.021610120
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  • 6
    Electronic Resource
    Electronic Resource
    True cosolvency. Acetone/diethylether/polystyrene (1973)
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 173 (1973), S. 241-245 
    Details
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/macp.1973.021730118
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  • 7
    Electronic Resource
    Electronic Resource
    Interdependence of enthalpic and entropic contributions to the second osmotic virial coefficient (1972)
    New York : Wiley-Blackwell
    Journal of Polymer Science Part A-2: Polymer Physics 10 (1972), S. 847-856 
    Details
    ISSN: 0449-2978
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The interdependence of the enthalpic contribution A2, H and the entropic contribution A2, s to the second osmotic virial coefficient for a given polymer-solvent system has been investigated from the experimental and the theoretical point of view. Experimentally, the following common facts were observed for various systems at temperatures and pressures below the critical values for the solvent. Both the isobaric and isothermal dependences can be approximated over relatively wide ranges of A2, H by linear relations with a slope deviating only slightly, but in a characteristic manner from a value of -1. When the temperature is increased at constant pressure one moves along an isobar towards higher A2, H; when the pressure is increased at constant temperature, one moves along an isotherm in the opposite direction, i.e., towards lower A2, H. Theoretically this behavior can be described in a qualitative manner, starting from a relation derived by Patterson and Delmas on the basis of the Prigogine corresponding-states theory. The reasons for the lack of quantitative agreement are discussed.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pol.1972.160100506
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  • 8
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    Mixed Conformations of Deoxyribonucleic Acid in Chromatin: A Preliminary Report (1972)
    National Academy of Sciences
    Details
    Publication Date: 1972-11-01
    Print ISSN: 0027-8424
    Electronic ISSN: 1091-6490
    Topics: Biology , Medicine , Natural Sciences in General
    Published by National Academy of Sciences
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  • 9
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    Sedimentation von gelösten Makromolekülen in der Nähe des kritische Punktes im Schwerefeld der Erde (1974)
    Springer
    Details
    Publication Date: 1974-04-01
    Print ISSN: 0372-820X
    Electronic ISSN: 1435-1536
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Published by Springer
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  • 10
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    Analysis of the duoplasmatron-type discharge as a source of multiply charged heavy ions (1974)
    Institute of Physics
    Details
    Publication Date: 1974-09-01
    Print ISSN: 0032-1028
    Topics: Physics
    Published by Institute of Physics
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