Characterization of Intramolecular Composition Heterogeneity of Metallocene‐Based and Conventional Ethylene‐Butene Copolymers using TREF/DSC

Abstract

A new and convenient method for the qualitative characterization of intramolecular composition heterogeneity was established. The metallocene-based and conventional ethylene-butene copolymers were fractionated with preparative temperature rising elution fractionation (TREF) technique, and some selected fractions were directly characterized with differential scanning calorimetry (DSC) after stepwise crystallization. The observed multiple endotherms in the melting traces of some fractions were attributed to intramolecular composition heterogeneity after other possibilities were excluded. It is found that intramolecular composition heterogeneity is present in both metallocene-based and conventional ethylene-butene copolymers, but the metallocene-based copolymers may have a relatively narrower intramolecular composition distribution. Moreover, the mechanism of this method and its applicable range are also discussed.