Decomposition of overlapped solid state sup (13) C NMR resonances belonging to different sterosequences in an atactic polymer.

We show for the first time clearly that the broad resonance of the alpha-methyl carbon observed in the CP MAS/DD sup (13) C NMR spectrum of atactic poly(methyl methacrylate) (PMMA) can be decomposed to three peaks corresponding to different tacticities (rr, rm (mr), and mm) by taking advantage of the differences in the rotational motions of the alpha-methyl carbons in these stereo-environments. We find the T sub 1's of the alpha-methyl carbons in atactic PMMA strongly depend on tacticity. The dependence of rotational motions on local conformation is discussed, and the cross polarization dynamics are also shown to reflect the local conformation. This method, which depends on tacticity related motional differences, can be applied to other atactic polymers in order to resolve overlapped solid state peaks into their individual stereoisomeric contributions.