Heterogeneous systems spin-lattice relaxation times

In heterogeneous polymer systems, nuclei with different mobilities and environments may have different relaxation times. This property has been widely exploited to study the partitioning of semi-crystalline polymers in their different phases. For example, measurements of the spin-lattice relaxation times of the crystalline portion of a set of polyethylenes have shown that the... 

However, a single Tt is generally observed in heterogeneous systems partly because it is difficult to resolve T2 components unless they differ by at least a factor of two. Deuterium T2 relaxation times in crosslinked resins, also exhibit only a singleexponential relaxation process, indicating that different 2H in the same molecule have essentially the same spin-lattice relaxation times44). 

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