Abstract
Two-dimensional exchange NMR is described and some recent applications to the study of slow rotational motions in solid polymers are reviewed. It is shown that each 2D NMR spectrum represents a statistically well-defined two-time distribution function characterizing the motional state of the system under study. The information available from 2D NMR is compared with that obtained from relaxation experiments and from neutron scattering. Experimental examples deal with ultraslow chain motions in the crystalline regions of poly(vinylideefluoride) and of amorphous poly(styrene) above its glass transition temperature, T g. It is shown that 2D exchange NMR and spin-lattice relaxation probe the α- and β-process, respectively, of the chain motion above T g separately.
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