Abstract
Several samples of polypropylene were fractionated by stepwise extraction with a series of solvents at their boiling points. The structural heterogeneity was estimated with the stereoreglarity parameter and the viscosity average molecular weight of the fractions. A correlation was obtained between these two quantities with the most of fractions except for those of low regularity. The tacticity of the intermediate fractions increased with their molecular weights, while that with high tacticity showed no dependence on the molecular weight. Though this relation in the intermediate part varied from sample to sample, it appeared to be related to their over-all regularities. The distributions of stereoregularity of the all samples polymerized with three component-catalyst system containing EtAlCl2 were found to be sharp.
Furthurmore, the results of the column fractional solution method at a constant temperature support the above conclusion, giving the information about the efficiency of the fractionation by solvent extraction.
