Carbon-13 NMR spectral assignments of regioirregular polypropylene determined from two-dimensional INADEQUATE spectra and chemical shift calculations

Abstract

The 13 C NMR spectrum of regioirregular polyropylene containing up to 40 mol% of inverted propylene units was assigned using the 2D INADEQUATE technique, the INEPT technique, and 13 C chemical shift calculations based on the 13 C NMR γ-effect and the application of the RIS model and also on the additive rules for 13 C chemical shifts of methyl-substituted alkanes. The presence of four kinds of sequences containing head-to-head and/or tail-to-tail units in the sample was confirmed. The 13 C- 13 C connectivities of the 2D INADEQUATE spectrum were extremely useful in the asssignment of overlapping peaks as well as the identification of several such sequences