Propene−Norbornene Copolymers. Toward a Description of Microstructure at Triad Level Based on Assignments of 13C NMR Spectra

A procedure for the quantitative determination of the molar fractions of the stereosequences defining the microstructure of a propene−norbornene (P−N) copolymer from 13C NMR spectra has been set up. This method utilizes the observed peak areas of the 13C signals and takes into account the consistency between peak areas and the stoichiometry of the copolymer chain. With the support of homonuclear 1H−1H and heteronuclear 1H−13C NMR techniques, by guessing assignments of unknown signals, and by discarding inconsistent hypotheses, an extension of signal assignments is made possible. This procedure, which allows for a quantitative analysis of copolymer sequences as accurate as possible, has been applied to the analysis of the 13C NMR spectra of a number of P−N copolymers prepared with catalyst precursors rac-Et(Indenyl)2ZrCl2 (1) and rac-Me2Si(2-Me-Indenyl)2ZrCl2 (2). A complete description of the microstructure at triad level, including 1,3- and 2,1-propene insertions, has been attempted. New signals have bee...