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

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 correspo…

Die Bestimmung der Molekulargewichtsverteilung von nichtkristallisierenden Polymeren mit dem Elektronenmikroskop, 4. Weiterentwicklung der Präparationsmethode durch Gefriertrocknung

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

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(methyl methacrylate) and the results are compared with those of GPC-measurements.

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

A mathematical treatment is described, by means of which the effect of the measuring errors on the number molecular weight distribution of polymers, as obtained with an electron microscope (EM), can be eliminated. It is shown, that the difference in the nonuniformities of the measured and the corrected distribution would be negligible only in the case of samples with high average degrees of polymerization and sufficiently broad distributions. Otherwise differences of 10% or more can be found, depending on the size of the actual measuring error. This is shown by means of four practical examples. For a practical application the measuring error may not exceed some critical value, which, though…