Berlin 2001 – wissenschaftliches Programm
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CPP: Chemische Physik und Polymerphysik
CPP 16: Poster: Dynamics of Molecular Systems, Polymer Dynamics, Glass Transition, Crystallization, Electronic Properties of Polymers
CPP 16.9: Poster
Montag, 2. April 2001, 12:30–15:00, AT1
Complex Dynamics as Probed by MAS NMR Methods: Approaching the Intermediate Motional Regime — •Kay Saalwächter1,2, Ingrid Fischbach1, and Hans Wolfgang Spiess1 — 1Max-Planck-Institut für Polymerforschung, Postfach 3148, D-55021 Mainz, Germany — 2Universität Freiburg, Institut für Makromolekulare Chemie, Stefan-Meier-Str. 31, D-79104 Freiburg, Germany
Novel high-resolution magic-angle spinning (MAS) nuclear magnetic resonance (NMR) methods are applied to the investigation of columnar discotic mesophases formed by hexabenzocoronene mesogens, and of shape-persistent polyphenylene dendrimers. Several 1H–13C double-resonance experiments, all based on radio-frequency recoupling of anisotropic NMR interactions, which are generally averaged out by the MAS, have recently been developed in order to probe motions on slow (s-ms) and fast (µs) timescales in such complex systems. A general problem concerning these techniques, as opposed to well-established 2H NMR, is a complex behavior and a concomitant loss of spectral intensity when correlation times approach the experimental timescale, i.e., the ms-µs range. We perform explicit pulse-sequence simulations based on numerical integration of the appropriate equation of motion, namely the stochastic Liouville-von-Neumann equation. Our results represent a first approach towards using the novel NMR methodology for the study of processes in the intermediate motional regime and give an indication of the feasibility and the limits of their application.