Verlag des Forschungszentrums Jülich
JUEL-3726
Krenzlin, Hans-Michael
Dynamics of complex molecules and multidimensional nuclear magnetic resonance
125 S., 1999
The relation between multidimensional Nuclear Magnetic Resonance (NMR)
techniques and the dynamical behaviour of complex molecules is considered in
this work. Two important NMR-interactions, the chemical shift and anisotropic
contributions in the case of restricted motions of molecules, are introduced
and discussed in two well-established models for polymer dynamics. Complex
molecules exhibit non-trivial time-dependent interactions between relaxing or
diffusing units. Dense polymer melts are considered, where the crossing of
chains is prohibited and excluded-volume interactions affect the dynamics.
Multidimensional NMR-techniques allow for the characterization and correlation
of molecular conformations at successive points in time. The notion of
"dimensionality" refers to the number of correlated points in time; here the
two-dimensional case is considered. In the first part of the thesis, analytical
investigations for a simplified model of polymer dynamics are presented.
A two-point correlation-function or, equivalently, a joint probability - with
which the outcome of a 2D NMR experiment can be compared - is calculated
for the Rubinstein-model. The results are displayed in histograms, which
have been designed according to 2D NMR spectra. In the second part of
the thesis, computer-simulations of a three-dimensional coarse grained model
for polymer dynamics were carried out. Monte-Carlo simulations of the bond-
fluctuation-model for chains of different length were performed with particular
emphasis on neighbourhood-conditions of monomers and bond-orientations.
The correlation-functions obtained were visualized in two-dimensional
spectra. From both models, information on local dynamical properties of polymer
chain segments was extracted and related to the effects on simulated 2D NMR
spectra.
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