VISCOELASTICITY AND SELF-DIFFUSION IN MELTS OF ENTANGLED LINEAR-POLYMERS

Dynamic properties in the melt state for two saturated hydrocarbon pol ymers, poly( ethylene-alt-propylene) (PEP) and head-to-head polypropyl ene (HHPP), were investigated by viscoelastic and diffusion measuremen ts, Several nearly monodisperse linear samples of each species were us ed. Zero-shear viscosity eta(o) and self-diffusion coefficient D varie d with temperature in accord with the WLF equation, and they also vari ed with molecular weight M in a manner that was consistent with the be havior of other species. The product eta(o)D was of particular interes t because extensive previous results for two other species, polystyren e and polyethylene, had led Pearson et al. to suggest that eta(o)D/(et a(o)D)(Rouse) is a universal function of the number of entanglements p er molecule M/M-e. With values far the Rouse model product for each sp ecies calculated from chain dimensions, and entanglement molecular wei ght from the plateau modulus, we show that the data for PEP and HHPP a lso support the Pearson universal form. (C) 1997 John Wiley & Sons, In c.