The overall composition of an ethylene-norbornene-copolymer can be determined by measuring the GPC-peak area, normalizing it according to sample weight and using a calibration curve established on the basis of 13C-NMR measurements. The normalized GPC-peak area decreases with increasing norbornene content up to 29-30 mol% when it disappears. At higher norbornene contents the polarity of the signal changes but the correlation with norbornene content is still valid. This phenomenon is due to refractive index changes caused by the comonomer. GPC is therefore a very practical tool for characterizing COC which has recently appeared on the market.
- comonomer content
- ethylene-norbornene copolymer