Berlin 2008 – scientific programme

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CPP: Fachverband Chemische Physik und Polymerphysik

CPP 34: POSTERS Polymerphysics

CPP 34.50: Poster

Thursday, February 28, 2008, 17:00–19:30, Poster A

Multiple-quantum NMR study of entangled polymer melt dynamics — •Fabian Vaca Chavez and Kay Saalwachter — Martin-Luther-Universität Halle-Wittenberg, Institut für Physik; Friedemann-Bach-Platz 6, D-06108 Halle (Germany)

Entangled polymers melts exhibit a variety of dynamic processes covering a wide range of time scales, starting form the fast segmental reorientation in the picoseconds scale up to the diffusive and cooperative motions in the range of seconds. NMR is a powerful tool to study molecular dynamics due to its sensitivity to different molecular motions. In particular, multiple quantum (MQ) NMR emerged a few years ago as a new and robust tool to study polymer chain dynamics [1]. This technique yields quantitative information in particular on chain ordering, i.e., on entanglement effects and crosslink densities, and on the timescale of chain motion. In this work, we apply MQ NMR to linear poly(cis -1,4-isoprene) and poly(dimethyl siloxane) over suitable ranges of well defined molecular weight and temperature, in order to establish the dynamic regimes predicted by the tube model, and obtain in in-depth comparison of the entangled dynamics of these polymers. The data is analyzed by establishing simple scaling laws [1], and full analytical expressions based on a correlation function which explicitly includes the Rouse and reptation dynamics [2].

[1] R. Graf, A. Heuer, H.W. Spiess, Phys. Rev. Lett., 80, 5738-5741 (1998).

[2] K. Saalwachter, A. Heuer, Macromolecules, 39, 3291-3303 (2006).