Molecular‐Weight Dependence of the Viscoelastic Properties of Whole Polymers

Abstract

A method has been developed by which it is possible to determine the type of molecular weight averaging upon which viscoelastic properties of polymers may depend and which may be used to verify the normal‐coordinate theory of viscoelasticity for various types of polymers. The method is extraordinarily simple to carry out since it involves only measurement of the property on whole polymers and mixtures of whole polymers. Neither fractionation nor molecular‐weight measurements themselves are required. Methods of determining the correct average‐molecular‐weight dependence of melt viscosity and steady‐state elastic compliance have been worked out in detail and are illustrated with data on linear polyethylenes. The method is also applicable to other polymer properties which are molecular‐weight dependent.