A rational measure for the heterogeneity of polymeric homologous substances

Abstract

AbstractA rational measure of the heterogeneity of high molecular substances is obtained by comparison of their molecular weight distribution with the theoretical distribution arrived at if infinitely large molecules are depolymerized in such a way that all linkages between the basic molecules are broken with equal ease. This distribution differs noticeably from the error function, which was used by Lansing and Kraemer in measuring heterogeneity. A table is given, by which the distribution curve can be transformed to a straight line. These table values, called “dist” values, are logarithms of the degrees of polymerization in the theoretical distribution, expressed in per cent of the median degree of polymerization. For a fractionated sample, the table values corresponding to the various percentages of substance at which the fractions were obtained are plotted versus the logarithms of the molecular weights. If the molecular weight distribution of the sample is similar to that in depolymerization, a straight line fits the points. The inverse value of the inclination of this line is a measure of the heterogeneity, for which the name heterogeneity quotient is suggested.