Estimation of Polymer Distribution on the Basis of Differences between the Average Molecular Weights of Different Order

Abstract

IT is well known that the magnitude of the difference between the number and weight average molecular weight (Mn and Mw) in a polymer affords an indication of the degree of polydispersity. In order to obtain a numerical measure of the spread of molecular weights, and to reconstruct the distribution, the assumption is often made—though admissible only under certain conditions—that the distribution function is that of the log normal law1–3, where the ratio between averages (the rth roots of the rth moments about zero) of successive order is an exponential function of the logarithm of the geometric standard deviation, which is equal to the standard deviation of the logarithmic distribution.