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  • 1
    Electronic Resource
    Electronic Resource
    Hoboken, NJ : Wiley-Blackwell
    Journal of Polymer Science 6 (1951), S. 381-382 
    ISSN: 0022-3832
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Hoboken, NJ : Wiley-Blackwell
    Journal of Polymer Science 8 (1952), S. 449-456 
    ISSN: 0022-3832
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The sedimentation equilibrium of polymers in mixed solvents at infinite dilution of polymer was analyzed by thermodynamic methods equivalent to those used by Stockmayer and Kirkwood and Goldberg for the light scattering case. It was found that the apparent weight-average molecular weight in a binary solvent mixture (when nonrefractometric methods are used to measure the experimental concentration gradient) is formally identical with that derived by Lansing and Kraemer on the assumption of stoichiometric combination of one of the solvents with the polymer. The “solvation number” now actually measures a preference for one solvent and can be expressed in terms of thermodynamic quantities characteristic of the ternary polymer-solvent system. In the case of refractometric measurements, where the two solvents have different refractive indices, refraction terms similar to those encountered in light scattering theory for mixed solvents also enter. Under equilibrium conditions, for polymer solutions in pure solvents, thermodynamics can say nothing about “solvation,” which is inseparable from the over-all nonideal behavior at finite concentrations. There is strong reason to believe that all types of experiments designed to measure solvation in mixed solvents under equilibrium conditions must give the same answer, since the same thermodynamic quantities determine polymer-solvent interactions in all cases. By assuming a dynamic equilibrium between sedimentation and diffusion in the equilibrium case and using the sedimentation term for the sedimentation velocity case, an expression for the sedimentation constant in mixed solvents at infinite dilution of polymer has been obtained. This expression is almost the same as that previously derived by Schachman and Lauffer, the difference occurring in an assumption about the density of solvated liquid made by these authors.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Hoboken, NJ : Wiley-Blackwell
    Journal of Polymer Science 11 (1953), S. 243-268 
    ISSN: 0022-3832
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: A study is made of the behavior under constant shear stress of several carefully characterized samples of polyisobutylene. The materials used are whole polymers and fractions obtained from these by dractional precipitation. As a first step in the characterization, the intrinsic viscosity of each is determined. It is shown that the samples cover a molecular weight range from 1 × 105 to 1 × 106. To provide a more detailed characterization, sedimentation equilibrium experiments are performed with several of the polyisobutylenes. These experiments yield values of several average molecular weights for each polymer, from which data an approximation to the molecular weight distribution can be made. It is pointed out that the whole polymers of isobutylene are very polydisperse. The viscosity-average molecular weights calculated from these experiments are in good agreement with the results of the intrinsic viscosity measurements. The viscoelastic behavior of some of these polymers is then studied by means of creep and recovery experiments. The melt viscosity is determined in two ways, from flow during creep and from the amount of nonrecoverable deformation after elastic recovery. The elastic recovery of the polyisobutylene samples is analyzed in some detail. A method for the reduction of data taken at several temperatures to a standard temperature, previously used for dynamic-mechanical properties and stress relaxation data, is shown to be applicable to elastic recovery data. Furthermore, the results of creep and recovery experiments can be superimposed in favorable cases. The steady-state elastic compliance is evaluated, and errors in its determination discussed. The results would seem to indicate that this quantity depends, at least in part, upon the degree of polydispersity of the polymer. This dependence appears to mask any direct variation with average molecular weight. Finally, it is shown that an average retardation time is directly proportional to the melt viscosity of the polymer.
    Additional Material: 17 Ill.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Hoboken, NJ : Wiley-Blackwell
    Journal of Polymer Science 12 (1954), S. 351-378 
    ISSN: 0022-3832
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: With the development of the ultracentrifuge by Svedberg there was provided a group of methods for the determination of solute molecular weight and of distribution of molecular weights in proper solutions. In addition to the sedimentation equilibrium and the sedimentation velocity experiments, there are other closely related molecular kinetic phenomena which, when taken together, form a collection of very useful tools in an area of macromolecular chemistry.The principal past use of the ultracentrifuge has been in the determination of the molecular weight and the homogeneity of proteins. In this report the attempt has been made to point the way for concerted action in the return to the original problem-that of investigating the dispersity of macromolecular and other colloidal solutions. Among other things, there is proposed in outline a combination of the sedimentation velocity and sedimentation equilibrium experiments to provide mass distribution data in macromolecular systems. While the main emphasis is devoted to the theory of the sedimentation methods and their unique usefulness to this end, there have been presented shorter discussions of diffusion and osmotic pressure as such and in their relationships to the sedimentation problems.Recognition is also made of the fact that the optical systems for the study of the redistribution of the components in the diffusion and sedimentation cells are now in a state of change, with a rapid adaptation of several interference methods to take the place of the more classical refractometric schemes. The change is being made in the interest of a greatly enhanced accuracy, even to the point that diffusion behavior in systems which contain two solutes can properly be observed.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Hoboken, NJ : Wiley-Blackwell
    Journal of Polymer Science 18 (1955), S. 445-446 
    ISSN: 0022-3832
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Hoboken, NJ : Wiley-Blackwell
    Journal of Polymer Science 13 (1954), S. 460-460 
    ISSN: 0022-3832
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Type of Medium: Electronic Resource
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