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60 Years after Flory’s Ideality Hypothesis: Are Polymer Chains in a Melt Really Ideal?
Jörg Baschnagel (Strasbourg)

14 janvier 2010

A cornerstone of modern polymer physics is the Flory ideality hypothesis. This hypothesis states that polymer chains in the melt—that is, in a liquid consisting of polymer chains—have random-walk-like conformations. The chains behave as if there were no excluded volume forces between the monomers. However, recent theoretical and numerical results suggest that this view of a polymer melt is an oversimplification. There are noticable deviations from chain ideality, resulting from the interplay of chain connectivity and incompressibility of the melt. This interplay leads to a swelling of chain segments and thus to a perturbation of the postulated ideal chain conformation. The swelling manifests itself, for instance, in the following way: (i) The bond-bond correlation function of two bonds separated by s monomers along the chain decays algebraically for large s instead of exponentially; (ii) there are systematic, wave-vector-dependent deviations from the Kratky plateau for the form factor of a chain; and (iii) the static Rouse modes are continuously depressed below the prediction for ideal chains. We will present an overview of these results and briefly discuss the relevance of the described deviations from chain ideality in other situations, e.g., for polymer melts in confined geometry.

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Jörg Baschnagel Jörg Baschnagel (Strasbourg)

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