Abstract
As shown by the numerous studies described in the literature, high-resolution 13C NMR has proven to be a most powerful tool for investigating local dynamics in polymers. Unlike fluorescence anisotropy or electron spin resonance techniques, it does not require any labeling of the molecule under study, and yields direct information on the compound under study. As a selective technique, it allows the observation of one signal per magnetically inequivalent carbon, and therefore the dynamic behaviour of each part of a molecule can be followed independently. Moreover, many NMR parameters are sensitive to molecular motions. They include the different relaxation times as well as the spectrum lineshape, the strength of the dipolar coupling and the chemical shift anisotropy. The available spectral windows depend on the type of measurement that is performed. They range from about 10-1 Hz for slow processes to several hundreds of MHz for very fast modes. In the case of bulk polymers at temperatures well above the glass-transition temperature, the fast processes of the local dynamics can be investigated by determining the spin-lattice relaxation time, T1, and the nuclear Overhauser enhancement, that probe modes in the Larmor frequency region, whereas measurements probing slower motions are more appropriate for glassy state investigations.KeywordsLocal DynamicDipolar CouplingBulk PolymerSpin DiffusionChemical Shift AnisotropyThese keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.
Published Version
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