Prediction of melt state poly(α-olefin) rheological properties:: The unsuspected role of the average molecular weight per backbone bond

It has previously been shown that the entanglement molecular weight (M-e) and the plateau modulus (G(N)(0)) of flexible polymers can be correlated to the unperturbed chain dimension, <R-2>(0)/M, chain density (rho) via the use of the packing length (rho), 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 G(N)(0) 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.