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Dresden 2011 – scientific programme

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CPP: Fachverband Chemische Physik und Polymerphysik

CPP 24: Poster: Polymer Dynamics

CPP 24.4: Poster

Tuesday, March 15, 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)

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