Monomer sequence distribution in ethylene‐propylene terpolymers measured by 13C nuclear magnetic resonance

Considerable progress has been made in the analysis of monomer sequence distribution in ethylene‐propylene copolymers and terpolymers. Fourier transform Carbon‐13 nuclear magnetic resonance spectra provide a significant increase in signal‐to‐noise over our previously published continuous wave (CW) spectra. Most of the methylene, methyl, and methine carbon resonances have been assigned and verified. A few uncertainties remain in the deconvolution of overlapping peaks or the prorating of coincident peaks for some of the minor constituent structures. For a series of four terpolymers containing approximately 1% ethylidenenorbornene as the third monomer, r1 r2 was determined to be 1.0. The precision is estimated to be better than ±0.2. The spectra contain enough data to ultimately provide several internal checks. When the methyl assignments are further refined, comparison may be made between the propylene sequence distributions calculated from methyl and from methine resonances. Devising a system for treating the effects of propylene inversion on the methylene resonances will allow description of the ethylene sequence distribution. The net result should be very reliable r1 r2 products for ethylene‐propylene copolymers and terpolymers of low third monomer content.