Carbon‐13 NMR spin‐lattice relaxation times of isotactic and syndiotactic sequences in amorphous polypropylene

Spin‐lattice relaxation times (T1) for methyl, methylene, and methine carbons in an amorphous polypropylene have been measured as a function of temperature from 46 to 138°C. The carbons from isotactic sequences characteristically exhibited the longest T1's of those observed. The T1 differences increased with temperature with the largest difference occuring for methine carbons where a 32% difference was observed. Activation energies were determined for the motional processes affecting T1's for isotactic and syndiotactic sequences with essentially no dependence upon configuration noted.