On the influence of excluded volume in polymer melts

Flory's ideality hypothesis states that polymer chains in the melt have random walk like conformations as if there would be no excluded volume. However, it was shown recently that the excluded volume interaction induces corrections to scaling which are long range and which give rise to a power law decay of bond-bond correlation function [1] as well as to corrections to the Kratky plateau of the form factor [2]. In this presentation, we focus on the Rouse mode analysis by switching on the excluded volume potential gradually to study the crossover from phantom chains (representing perfect random walks described by the Rouse model) to real polymer melts [3]. In the melt, significant corrections have to be made to the static Rouse mode spectrum and consequences for the dynamics are briefly discussed. This gives also evidence that subdiffusive behaviour found in contradiction to the Rouse model is also caused by the excluded volume interaction. [1] J. Wittmer, H. Meyer, J. Baschnagel et. al. Phys. Rev. Lett. 93 (2004) 147801. Phys. Rev. E 76 (2007) 011803. [2] J. Wittmer et. al. EPL 77 (2007) 56003. [3] H. Meyer et. al. accepted at Eur. Phys. J. E (2007)