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  • Polymer and Materials Science  (28)
  • 1
    Electronic Resource
    Electronic Resource
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 171 (1973), S. 135-144 
    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 Temperaturabhängigkeit der Lichtstreuungs- und Viskositätsdaten wurde an drei Polymeren: Poly(4-bromphenyläthylen) [Poly(p-Bromostyrol)], Poly[1-(methoxycarbonyl)-1-methyläthylen][Poly(methylmethacrylat)] und Poly(2-pyridyläthylen)[Poly(2-vinylpyridin)] in verdünnter Lösung gemessen. In einem engen Temperaturbereich treten starke Änderungen der zweiten Virialkoeffizienten, der ungestörten Dimensionen und der Streulichtintensitäten auf. Diese Beobachtungen sind auf eine Konformationsänderung der Kette, die in den gewählten Lösungsmitteln auftreten, zurückzuführen. Innerhalb der betrachteten Temperaturbereiche steigt die Flexibilität der Kette rasch an.Diese Konformationsübergänge verschwinden, sobald man kleinere Mengen an polaren, die Kette solvatisierenden Lösungsmitteln zugibt. Das beweist, daß die beobachteten Phänomene mit den „short range“-Wechselwirkungen verknüpft sind.
    Notes: Temperature dependence of light scattering and viscosity data was studied on three polymers: poly(4-bromophenylethylene) [poly-p-bromostyrene], poly[1-(methoxycarbonyl)-1-methylethylene] [poly(methyl methacrylate)] and poly(2-pyridylethylene) [poly(vinylpyridine)] in dilute solution. It was observed that over a narrow range of temperature sharp changes of second virial coefficients, unperturbed dimensions and scattered intensities do occur. This phenomenon can be accounted for by assuming that in the chosen solvents the conformation of the chain undergoes changes, increasing temperature causing a higher flexibility.These conformational changes disappear entirely on addition of minute amounts of well solvating, polar solvents, which confirms that the observed transition is only concerned with short range interactions along the chain.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
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  • 2
    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: This paper describes the study of preferential adsorption of polystyrene in a solvent mixture as a function of different parameters. In the first place the influence of the density of intramolecular segments (the effect of the molecular weight and the polydispersity of the polymer) on this phenomenon was examined. The effect of the temperature on the solvation coefficient was also considered. Certain experimental results were found to be in good agreement with the thermodynamic theories of preferential adsorption. The lack of the knowledge concerning the variation of the thermodynamic interaction parameters, with the density of intramolecular segments and the temperature, did not permit a rigorous quantitative study.
    Notes: Dans cet article nous présentons les résultats d'une étude de l'adsorption préférentielle du polystyrène en mélange de solvants en fonction de différents paramètres. En premier lieu, nous avons examiné l'influence de la densité en segments intramoléculaire (effet de la masse moléculaire et de la polydispersité du polymère) sur ce phénomène. L'effet de la température sur le coefficient de solvatation a également été considéré. Pour certains de nos résultats expérimentaux, il existe un bon accord avec les théories thermodynamiques de l'adsorption préférentielle, cependant le manque de connaissances relatives à la variation avec la densité en segments intramoléculaires et la température, des paramètres d'interaction thermodynamiques, ne permet pas une étude quantitative rigoureuse.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
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  • 3
    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: The preferential adsorption coefficient of a polymer in dilute solution of a mixture of solvents is a function of the mean density of intramolecular segments. This effect, already shown in the case of linear polystyrenes in binary solvents, was observed with branched polystyrenes of star and comb structure, which may attain important local densities in a benzene/methanol mixture. A relation of the type: \documentclass{article}\pagestyle{empty}\begin{document}$$ \lambda = \lambda _\infty + a\langle v_3 \rangle + b\langle v_3 \rangle ^2 $$\end{document} (〈v3〉 being the mean intramolecular volume fraction of the polymer), established by means of thermodynamic theories of solvation equilibrium, permits to explain the experimental results.A comparative study of adsorption coefficients of branched polystyrene and linear polystyrene of the same molecular weight, made it possible, in certain particular cases, to determine the structural parameter g of branched polystyrene.
    Notes: Le coefficient d'adsorption préférentielle en solution diluée d'un polymère en mélange de solvants, est une fonction de la densité moyenne en segments intramoléculaire. Cet effet, déjà mis en évidence pour des polystyrènes linéaires en solvants binaires, a été observé pour des polystyrènes ramifiés à structure en étoile et en peigne, pouvant atteindre des densités locales importantes, dans le mélange benzène/méthanol. Une relation du type: \documentclass{article}\pagestyle{empty}\begin{document}$$ \lambda = \lambda _\infty + a\langle v_3 \rangle + b\langle v_3 \rangle ^2 $$\end{document}(〈v3〉 étant la fraction en volume moyenne intramoléculaire du polymère), établie à partir des théories thermodynamiques de l'équilibre de solvatation, permet de rendre compte des résultats expérimentaux.Une étude comparative des coefficients d'adsorption de polystyrènes ramifiés et des polystyrènes linéaires de měme masse moléculaire, a permis dans certains cas particuliers, de déterminer le paramètre de structure g du polystyrène ramifié.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 184 (1983), S. 2153-2158 
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: A very sharp crossover is observed in the variation of the reduced viscosity ηsp/c as a function of the concentration c for mixtures of 1:1 by weight mixtures of polystyrene and poly(methylmethacrylate) in benzene at 20°C and a 1:1 by weight mixture of poly(ethylene glycol) and polystyrene in benzene at 20°C. The crossover is attributed to the critical to the concentration of the two respective polymers in the solution and its sharpness is due to the incompatibility between the two different polymers.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 170 (1973), S. 165-176 
    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: The lowering of the Θ-temperature observed for branched polystyrenes in cyclohexane is extended to other systems: polystyrene in diethyl malonate, in decaline and in a mixed solvent (78% benzene/22% methanol), and to some other polymers such as polyisoprene in methyl propyl ketone and poly(vinyl acetate) in 3-heptanone and ethanol.The temperature ΘA2 (measured by light scattering), and the precipitation temperature Tp (measured by liquid-phase separation) of these polymers are always lower than for linear polymers of the same chemical nature. The Θ-temperature decreases with increasing degree of branching.
    Notes: L'abaissement de la temperature Θ observé pour les polystyrènes ramifiés dans le cyclohexane est généralisé a d'autres systèmes: polystyrène dans 1e malonate d'éthyle, la décaline et un mélange de solvants (benzène 78%, méthanol 22%)  -  ainsi qu'à d'autres polymères tels que le polyisoprène dans la méthylpropylcétone et l'acétate de polyvinyle en solution dans la heptanone-3 et l'éthanol.La température ΘA2 (mesurée par diffusion de la lumière) et la température de précipitation Tp (mesurée par méthode de séparation de phase) de ces polymères est inférieure dans tous les cas à celle des polymbres linéaires de même nature chimique. L'abaissement ΔΘ observé croit avec le degré de ramification.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 176 (1975), S. 3441-3451 
    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: Some theoretical considerations and experimental results are presented on the limiting viscosity number of polystyrene, (PS), dissolved in a mixture of poly(methyl methacrylate), (PMMA), and p-xylene, and of PMMA in a mixture of PS and p-xylene. At relatively low concentration, this problem can be treated using the classical formalism of dilute solutions, introducing in addition a new parameter bAB characterizing the interactions between the polymers A and B. The quantitative use of this apparently simple method involves some difficulties owing to the fact that terms of higher order have to be taken into account even at moderate concentrations.The results can be explained by a decrease of the polymer dimensions which is more pronounced when the “solvent polymer” is of low molecular weight.At higher concentration, there is a critical point which seems to appear when the total volume of the two polymers is equal to the volume of the solution.
    Notes: Dans ce travail sont présentés quelques résultats expérimentaux et quelques considérations théoriques concernant l'indice limite viscosimétrique du polystyrène, (PS), dissous dans un mélange de poly(méthacrylate de méthyle), (PMMA), et de p-xylène, et de PMMA dissous dans un mélange de PS et de p-xylène. A une concentration relativement basse, on peut essayer d'interpréter ces systèmes en faisant appel au formalisme des solutions diluées et en introduisant un coefficient d'interaction bAB entre les deux polymères A et B. Cette voie, qui semble la plus simple, est difficile à utiliser quantitativement. car měme pour des concentrations modérées, il faut considérer des termes d'ordre supérieur.Les résultats obtenus peuvent ětre expliqués par une diminution des dimensions du polymère qui est plus prononcée quand le «polymère-solvant» est de petite masse moléculaire.A une concentration élevée, il apparaǐt un point critique qui semble se manifester quand le volume total de la solution est occupé par les deux polymères.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 178 (1977), S. 1089-1097 
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: In this paper we have been studying the effect of concentration c on reduced viscosity ηsp/c for a triblock copolymer poly(methyl methacrylate)/polystyrene/poly(methyl methacrylate) and for a graft copolymer of the same nature.The temperature of the experiments has been chosen in the range where the conformation changes from a segregated form to a pseudogaussian one. For this temperature range ηsp/c is not a linear function of concentration but the points ηsp/c vs. c are situated on two straight line segments with a well defined intercept.We discuss the phenomenon in comparison to results obtained on mixtures of homopolymers. These results suggest a strong and anomalous dependance of molecular conformation on concentration.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
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  • 8
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: It is shown that small quantities of poly(2-vinylpyridine) extensively change the coexistence curves of the two liquids methanol/cyclohexane, especially in the vicinity of the critical point of the two liquids. It is possible to observe as a function of temperature two domains of solubility separated by three domains of precipitation when the polymer has a molecular weight 200 000. Moreover the dimensions of the dissolved poly(2-vinylpyridine) are abnormally high in the region of the critical point of the two liquids.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 4 (1981), S. 85-99 
    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
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  • 10
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Block copolymers poly(methyl methacrylate)-block-polystyrene-block-poly(methyl methacrylate) and polystyrene-block-poly(tert-butyl methacrylate) were prepared by anionic polymerization and were studied in dilute solution as well as in the bulk state. The viscometric study revealed that the block copolymers exhibit a conformational “transition” occurring in a narrow temperature range. Films were obtained with the same copolymers by casting at different temperatures, chosen below and above the “transition”. From the investigation of these films by differential scanning calorimetry, using the entropy relaxation method, and by dynamic mechanical measurements, it was shown that the block copolymers exhibit a rather segregated structure if they are obtained below the “transition” temperature, and that they adopt a quasi-Gaussian conformation (implying a better miscibility of the two kinds of blocks) if the solvent is evaporated above the “transition” temperature.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
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