Improved quantitative solution state 13C NMR analysis of ethylene-1-octene copolymers

Abstract

In order to acquire fully quantitative, high signal-to-noise 13C NMR spectra of ethylene-1-octene copolymers in a relatively short period of time, a detailed protocol has been developed, based on the addition of an optimised amount of the relaxation agent chromium(III)triacetylacetonate and without using nuclear overhauser enhancement (NOE). Compared to classical measurements with NOE, the proposed measuring protocol additionally offers a gain in signal-to-noise of 16%, which corresponds to a gain in experimental time of 34%. It allows precise and accurate quantification of all resonances, including small one's related to, e.g. comonomer inversion, and offers more refined information towards the determination of chemical shift and peak area measurements and the development of statistical chain microstructure models.