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Jeudi 14 janvier
Résumé :
A cornerstone of modern polymer physics is the Flory ideality
hypothesis. This hypothesis states that polymer chains in the meltthat is,
in a liquid consisting of polymer chainshave random-walk-like conformations.
The chains behave as if there were no excluded volume for ces between the
monomers. However, recent theoretical and numerical results suggest that
this view of a polymer melt is an oversimpli-cation. 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 brie
y discuss the relevance of the described deviations from
chain ideality in other situations, e.g., for polymer melts in con-ned geometry.
RECRUTEMENT ACCES DIRECT
Le département de physique
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