Prediction of Melt State Poly(α-olefin) Rheological Properties:  The Unsuspected Role of the Average Molecular Weight per Backbone Bond

Abstract

It has previously been shown that the entanglement molecular weight ( M e ) and the plateau modulus ( ) of flexible polymers can be correlated to the unperturbed chain dimension, 〈 R 2 〉 0 / M, chain density (ρ) via the use of the packing length ( p ), which is defined as the volume of a chain divided by its mean square end to end distance. For polyolefins and co-polyolefins where 〈 R 2 〉 0 / M remains unmeasured a method is presented herein where knowledge of the average molecular weight per backbone bond ( m b ) allows and thus M e to be estimated. This is particularly valuable for the case of polyolefin copolymers where the melt chain dimensions (and thus the packing length) are unknown.