UNDECAD RESOLUTION OF POLYPROPYLENE STEREOSEQUENCES - QUANTITATIVE-EVALUATION OF C-13 NMR METHYL SPECTRUM

The quantitative evaluation of a 50.3 MHz 13C NMR methyl spectrum of a particular stereoisomer of polypropylene, called hemiisotactic (hit-PP), was performed by a full lineshape fitting procedure. This sample presents a dramatic selection between stereosequences and a characteristic pattern of signal intensities. The results are compared with a general statistical approach, leading to the conclusions that the structure of hit-PP is almost pure (96%). Also, small deviations from the ideality are accounted for. In this way linewidths and chemical shifts have been established for nine nonads and five undecads of monomer units, calling for a sensitivity to carbon atoms distant up to ten bonds.