AbstractThe absorption band at 1378 cm−1was used for the quantitative determination of branching in polyethylene. Using various models with different alkyl groups (12‐alkyltriacosanes, 11,20‐dialkyltriacontances, alkylcyclohexanes, homopolymers), new absorption coefficients, depending on their branching, were obtained. The degrees of branching of a series of copolymers deriving from α‐olefins (15 compounds) determined by infrared spectroscopy with the new coefficients and by13C NMR spectroscopy were