Carbon‐13 nuclear magnetic resonance of ethylene–propylene copolymer and the determination of sequence distribution of monomeric units

The 13C‐NMR spectra of ethylene–propylene copolymers and their model compounds were measured at 15.1 MHz. Assignments of the signals were carried out by using the equation of Grant and Paul and also by comparing the spectra with those of squalane, hydrogenated natural rubber, polyethylene, and atactic polypropylene. The accuracy and the precision of intensity measurements, that is, the deviation from the theoretical values and the scatter of the measurements, respectively, were checked for the spectra of squalane and hydrogenated natural rubber and were shown to be at most 12% for each of the signals. On the basis of these results the mole fractions of the four types of the dyad sequences, that is, the propylene–propylene (head‐to‐tail and head‐to‐head), the ethylene–propylene, and the ethylene–ethylene sequences, were determined together with the average sequence lengths of both monomer units.