INTERMOLECULAR STRUCTURAL HOMOGENEITY OF METALLOCENE POLYETHYLENE COPOLYMERS

Direct proof of intermolecular compositional inhomogeneity of a metall ocene polyethylene copolymer has been obtained using a cross-fractiona tion (CF) technique. The ethylene/1-hexene copolymer sample was synthe sized using a Zr-based homogeneous metallocene catalyst. A solvent gra dient fractionation (SGF) applied to the whole polymer material has pr oduced nearly monodispersed molecular weight distribution fractions. T he component molecules of a representative SGF fraction are then furth er sorted out, using a temperature gradient fractionation technique, a ccording to their short-chain branching (SCB) differences. Molecular c haracterization of the resulting CF fractions reveals the presence of significant intermolecular SCB content differences among the component s of the sample material.