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We have shown in previous studies that the entanglement molecular weight for a polymer melt, M e, is related by a power law to p, the packing length of the polymer species. We now find that power laws also describe the molecular weights characterizing the melt viscosity, M c marking the onset of entanglement effects and M r the crossover to the reptation form. The packing length exponents for M e, M c, and M r differ significantly, however. The long-held notion that the ratio M c/M e has the same value for all species is therefore incorrect. Further, the observed and predicted values of M r for two species, 1,4-polybutadiene and polyisobutylene, have been found to agree, within the uncertainties, with the projected values. Finally, the variations with packing length are such that all three characteristic molecular weights would appear to converge on the same value near p = 9 Å. As yet, no species with such a large packing length has been completely studied rheologically. But the range is not outlandish and is clearly reachable by appropriate synthetic methods.

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In this article, we reexamine and extend a relationship proposed earlier between entanglement density and chain dimensions in polymer melts. The power‐law equation presented in the earlier work, relating the entanglement molecular weight Me, melt chain density ρ, and the packing length p is tested with additional polymer species. Now included are additional polydienes and 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 poly(methacrylates), and polymeric sulfur. We find that within experimental uncertainties, Me/ρ and p are related through an equation (Me/ρ = 218p3) that is insensitive to temperature (25°C ≤ T ≤ 380°C) and which seems to be universal for flexible Gaussian chains in the melt state. © 1999 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 37: 1023–1033, 1999

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The third edition of this well known textbook discusses the diverse physical states and associated properties of polymeric materials. The contents of the book have been conveniently divided into two general parts, 'Physical States of Polymers' and 'Characterization Techniques'. Written by seven of the leading figures in the polymer science community, this third edition has been thoroughly updated and expanded. As in the second edition, all of the chapters contain general introductory material and comprehensive literature citations designed to give newcomers to the field an appreciation of the subject and how it fits into the general context of polymer science. Containing numerous problem sets and worked examples this third edition provides enough core material for a one semester survey course at the advanced undergraduate or graduate level.

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