Exchange spectra of isotactic polypropylene

The elaboration of this experiment to three dimensions can be readily seen by imagining an additional mixing time and a vertical slice perpendicular to the cross-peak, noted above. The peaks in this imaginary slice would result 

Eight possible isomerizations could occur for the pinned tg + tg- conformation. Four of these isomerizations involved reorientation angles of about 67° or 113° and were consistent with the NMR data. However, each of the four motions implied a different electric dipole moment and only one of these tg + tg- to g-tg + ) was consistent with dielectric data. Therefore, from a combination of NMR data and dielectric data it was possible to uniquely determine the particular mechanism for reorientation of PVF2 although neither of these methods would determine the reorientation mechanism alone. 

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