Relaxation molecular/segmental

Usually, nuclear relaxation data for the study of reorientational motions of molecules and molecular segments are obtained for non-viscous liquids in the extreme narrowing region where the product of the resonance frequency and the reorientational correlation time is much less than unity [1, 3, 5]. The dipolar spin-lattice relaxation rate of nucleus i is then directly proportional to the reorientational correlation time p... 

Finally, it is worth while to consider the applicability of these relaxation methods to molecules having flexible conformations. Examples given in the previous Section demonstrated that relaxation rates are able to define either the most probable conformation of a flexible molecular segment, or to specify a range of allowed conformations from the total number of confor-... 

Strong intermolecular interactions such as hydrogen bonds or ion-dipole pairs restrict the motion of molecules and pertinent molecular segments. These interactions increase the correlation time zc and accelerate the 13C spin-lattice relaxation. Shorter 13C relaxation times can therefore also indicate the presence of such interactions. The Tj values of the C atoms of carboxylic acids, phenols, alcohols, and solvated molecular ions behave in this way. 

On balance, the ii relaxation process is now regarded as involving partially-correlated motion of a moderate number of molecular segments or repeat units as... 

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