Etude par 13C NMR d'alcanes lourds mono‐ et diramifiés. Modèles de polyoléfines

13C NMR spectra were obtained for a series of branched, heavy alkanes at 37°C and 100°C, which provide a model set for describing the branched sequences in low density polyethylene (LDPE) and copolymers of α-olefines. In addition, they provide a model set for revising the empirical Grant-Paul and Lindeman-Adams additive coefficients and corrective terms for pre-dicting 13C chemical shifts of alkanes. The resulting revised parameters (for 37°C and 100°C) produce more accurate predictions of 13C NMR spectra for branched alkanes and it is noted that some corrective terms can be temperature-sensitive.