High resolution solid state sup (13) C NMR study of isotactic polypropylene polymorphs.

High resolution sup (13) C NMR spectra are reported for three solid samples of isotactic polypropylene (1-PP): 1) the alpha- crystalline form (monoclinic), 11)the beta-crystalline form (hexagonal), and 111) the mesomorphic or smectic form of 1- PP. These spectra were obtained using magic angle spinning, high power proton dipolar-decoupling, and cross-polarization techniques, and for the beta-and smectic-forms of 1-PP constitute the first reported high resolution solid-state spectra. The spectrum of the alpha-crystalline form shows well-resolved splittings (1 ppm) of the methyl and methylene carbon resonances, as was reported previously by Bunn et al. These splittings are absent in the spectra observed for the beta- and smectic- forms of 1-PP.