New Interpretations: Molecular Weight Averages for a Polymer
Chong Wha Pyun, Hershel Markovitz · Journal of Macromolecular Science Part A - Chemistry · 1977
The statement is often made in the polymer literature, without proof, that M z ≤ M w ≤ M n, where M z, M w, and M n are the z-, z weight-, and number-average molecular weights respectively. Four proofs of a generalization of these inequalities are given. It is shown that a higher-order molecular weight average is larger than a lower-order one, regardless of the form of the molecular weight distributions, except for the case when all the molecules have the same molecular weight. A brief discussion of the viscosity-average molecular weight is also included.