Die Bestimmung der Molekulargewichtsverteilung von nichtkristallisierenden Polymeren mit dem Elektronenmikroskop, 6. Fehlerkorrektur der experimentellen Zahlenverteilungsfunktion

Koszterszitz, G.; Greschner, Georg S.; Schulz, G. V.

doi:10.1002/macp.1977.021780418

Cited by 5 publications

(1 citation statement)

References 4 publications

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“…The polydispersity of a sample is reflected in the width of the sedimentation boundary. By looking at the entire boundary, a distribution of sedimentation coefficients g(s) is therefore observed:22,23 g(s) = dc/ds = (dc/dr)(dr/ds) which can be transformed into a MWD w(M) = (ds / dAf) (dc / dr) (dr / ds) (7) with eq 4 and 6.…”

Section: Ultracentrifuge Measurementsmentioning

confidence: 99%

Characterization of Polystyrenes of Extremely High Molecular Weights

Appelt¹,

Meyerhoff²

1980

Macromolecules

929

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An extensive effort to characterize polystyrenes of a wide range of molecular weights of up to M, = 40 X lo6 by a variety of different methods is reported. The employed methods of investigation, such as frequency analyzing (dynamic) and frequency averaging (classical) light scattering, velocity sedimentation, and viscometry, always lead to linear double-logarithmic relationships between the obtained quantities and the molecular weight. Molecular weight distributions of several samples in the same molecular weight range were investigated as well by classical light scattering, velocity sedimentation, and GPC. Comparison of the results, also with fractionation data, gives good agreement between the different methods and demonstrates the usefulness of some new approaches.Until recently, synthetic polymers of extremely high molecular weights have only been of limited interest to the scientific world, even though an extension of the molecular weight scale by one or two decades might provide a crucial experimental test for some theoretical equations, e.g., relating the conformation to the excluded volume.There are, however, a number of problems associated with the investigation of the properties of extremely high molecular weight polymers: For one, the systematic preparation of such polymers requires in general a rather refined experimental technique which must meet the most stringent purity specifications, irrespective of the mode of synthesis. Anionic polymerization has been advanced systematically to yield polystyrenes in the molecular weight range of M , = 13 X lo6 with narrow molecular weight distributions (MWD).' Earlier, McIntyre et ala2 had been successful in obtaining an anionic polystyrene of M , = 44 X lo6. Emulsion polymerization just recently yielded a polystyrene of M , = 57 X lo6 after fra~tionation.~ Purely thermal polymerization of styrene at low temperatures to low conversion leads to polymers of similarly high molecular weights ( M , = 35 X lo6 ~nfractionated).~ Spontaneous thermal polymerization of methyl methacrylate at lower temperatures produces polymers in the same or possibly higher molecular weight range.5 The latter two modes of polymerization yield molecular weight distributions of M,/M,, = 2, since their molecular weights are regulated by transfer reactions to an intermediate and/or the monomer, respectively.

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Section: Ultracentrifuge Measurementsmentioning

confidence: 99%

Characterization of Polystyrenes of Extremely High Molecular Weights

Appelt¹,

Meyerhoff²

1980

Macromolecules

929

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Die Bestimmung der Molekulargewichtsverteilung von nichtkristallisierenden Polymeren mit dem Elektronenmikroskop, 5. Bestimmung der Masse der Einzelmoleküle und Aufnahme der Molekulargewichtsverteilung

Koszterszitz

Schulz

1977

Makromol. Chem.

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A method is described for the determination of the molecular weight distribution (MWD) of various polymers from electron microscopy pictures of their molecules. It is shown, that the number of molecules needed to construct the distribution is between 200 and 300. Furthermore, with macroscopic density of the polymer and the volume determined by electron microscopy, the correct mass of a single molecule is obtained. The method is demonstrated for samples of polystyrene and poly(methy1 methacrylate) and the results are compared with those of GPC-measurements. I . EinleitungIn unserer vorangehenden Mitteilung" wurde beschrieben, wie die einzelnen Molekule eines makromolekularen Stoffes aus einer sehr verdunnten Losung durch Gefriertrocknung auf einer Unterlage abgeschieden und durch Schragbedampfung im Elektronenmikroskop (EM) sichtbar gemacht werden konnen. In dieser Mitteilung wird gezeigt, daB man aus dem gemessenen Durchmesser und aus der gemessenen Schattenlange das Volumen der einzelnen Teilchen berechnen kann. Daraus ergibt sich unter Annahme einer bestimmten Dichte -wir setzen dafur die makroskopische Dichte des gesamten Praparates ein *I 4. Mitteilung: cf.".

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Die bestimmung der molekulargewichtsverteilung von nichtkristallisierenden polymeren mit dem elektronenmikroskop, 7. Präparation durch verdampfung des lösungsmittels aus lösung

Koszterszitz

Schulz

1977

Makromol. Chem.

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A preparation method is described by means of which it is possible to transfer individual molecules of a high molecular weight polymer on a support, in order to determine their mass and therefrom their molecular weight distribution, using our previously published electron microscopic method.The advantages of the new procedure as compared to the previously described freeze-drying are 1) that the range of solvents, which can be used is much larger, and 2) that the preparation is performed by evaporation from a dilute solution, which means that the molecules are distributed statistically on the support. The risk of formation of associates is avoided by keeping the polymer concentration correspondingly low and the rate of evaporation high. As examples the results for three samples of poly(methy1 methacrylate) and one sample of natural rubber are reported and discussed.

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Die Bestimmung der Molekulargewichtsverteilung von nichtkristallisierenden Polymeren mit dem Elektronenmikroskop, 6. Fehlerkorrektur der experimentellen Zahlenverteilungsfunktion

Cited by 5 publications

References 4 publications

Characterization of Polystyrenes of Extremely High Molecular Weights

Characterization of Polystyrenes of Extremely High Molecular Weights

Die Bestimmung der Molekulargewichtsverteilung von nichtkristallisierenden Polymeren mit dem Elektronenmikroskop, 5. Bestimmung der Masse der Einzelmoleküle und Aufnahme der Molekulargewichtsverteilung

Die bestimmung der molekulargewichtsverteilung von nichtkristallisierenden polymeren mit dem elektronenmikroskop, 7. Präparation durch verdampfung des lösungsmittels aus lösung

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