Dresden 2011 – wissenschaftliches Programm

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CPP: Fachverband Chemische Physik und Polymerphysik

CPP 24: Poster: Polymer Dynamics

CPP 24.4: Poster

Dienstag, 15. März 2011, 18:00–20:00, P2

Multiple-quantum NMR observations of constraint release and contour-length fluctuation — •Marie-Luise Lehnich and Kay Saalwächter — Institut für Physik-NMR, Universität Halle, Betty-Heimann-Str. 7, 06120 Halle

The behaviour of entangled melts is still not fully understood. The predictions of de Gennes’ famous reptation concept can be observed directly with ¹H multiple-quantum NMR. We monitor the dynamics of long-chain polymer melts over 5 decades in time. The regimes II-IV of the tube model are covered with this technique. The fixed-tube model, which is a combination of Rouse theory for unentangled melts and the reptation model, describes the mechanical data insufficiently. This causes ongoing discussions on also including the dynamics of the tube itself. Contour-length fluctuations (CLF) and constrained release (CR) could be the reason for the motion of the tube.

In extending previous work [1], we diluted protonated chains in matrices of deuterated chains, which are invisible in ¹H NMR. With this method, the influence of the "tube" can be analysed in an isolated fashion. The effects of CR and CLF can be separately studied.

[1] F. Vaca Cháves and K. Saalwächter. NMR Observation of Entangled Polymer Dynamics: Tube Model Predictions and Constrained Release, Phys. Rev. Lett., 104, 198305 (2010)