Chain dimensions and entanglement spacings in dense macromolecular systems

In this article, we reexamine and extend a relationship proposed earlier be tween entanglement density and chain dimensions in polymer melts. The power -law equation presented in the earlier work, relating the entanglement mole cular weight M-e, melt chain density rho, and the packing length p is teste d with additional polymer species. Now included are additional polydienes a nd their hydrogenated derivatives, the isotactic forms of polypropylene and polystyrene, the essentially syndiotactic form of poly(methyl methacrylate ), along with poly(tetrafluoroethylene), poly(vinylmethyl ether), various p oly(methacrylates), and polymeric sulfur. We find that within experimental uncertainties, M-e/rho and p are related through an equation (M-e/rho = 218 p(3)) that is insensitive to temperature (25 degrees C less than or equal t o T less than or equal to 380 degrees C) and which seems to be universal fo r flexible Gaussian chains in the melt state. (C) 1999 John Wiley & Sons, I nc.