Determination of monomer sequence distribution in EPDM by ¹³C-NMR: Third monomer effects

The methods for sequencing ethylene–propylene copolymers (EPMs) by ¹³C-NMR were extended to account for third monomer effects. The equations for calculating the ethylene content and monomer sequence distribution in EPMs were corrected for the presence of the third monomers 1,4 hexadiene, 2-ethylidene-5-norbornene, and 5,8-dicyclopentadiene that display resonances that overlap with the main chain EPM carbons. These corrections dramatically reduce the standard deviation among equivalent calculation methods. We also examined the effects of experimental conditions on the sequencing data including the choice of solvent, Cr³⁺ doping, and the presence of the nuclear Overhauser effect. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 71: 523–530, 1999