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FUNDAMENTAL RESEARCHES ON THE FRACTIONATION OF HIGH POLYMERS. I. ON THE ABSOLUTE EVALUATION OF THE FRACTIONATION CURVES.
FOREIGN TECHNOLOGY DIV WRIGHT-PATTERSON AFB OH
The molecular weight distributions of four polymethylmethacrylate fractions were studied by column elution chromatography and by the sedimentation rate method in an ultracentrifuge. The criterion for the absolute evaluation of the molecular weight distribution curves obtained is based on the superposibility of the distribution curves of single fractions to give the distribution curve of a mixed fraction. The solvents used for gradient elution were benzene-methanol, while ultracentrifuge sedimentation was observed in acetone-ethanol in the vicinity of the Theta-temperature of the polymer-solvent system. The experimental results indicate that the fractionation curves from elution chromagraphy gave too narrow a distribution of molecular weights, while the sedimentation rate method gave very satisfactory results. It is concluded that if the conventional method of calculating the integral distribution curve from the fractionation data is used, the high molecular weight tail of the distribution curve is greatly understimated. A better procedure for evaluating the fractionation data with due allowance for the molecular weight distribution within each fraction remains to be devised. Author
Trans. from Hua Hseuh Hsueh Pao (Acta Chimica Sinica), 27:2, pp. 147-154, 1961.