MOLECULAR-STRUCTURE OF STYRENE-ETHYLENE COPOLYMERS PREPARED OVER DIFFERENT KINDS OF TITANIUM CATALYSTS

The copolymerization of styrene and ethylene was carried out in the pr esence of two different catalyst systems; i.e., CpTiCl3-methyl alumino xane and TiCl4-methyl aluminoxane. The structure of polymers was inves tigated with C-13-NMR (nuclear magnetic resonance) spectroscopy, DSC ( differential scanning calorimetry) and XRD (X-ray diffractometry). Fro m the analyses of the C-13-NMR and XRD data, the molecular structure o f the styrene-ethylene copolymer produced over the CpTiCl3 catalyst sy stem seems to indicate that the ethylene units are randomly distribute d in the syndiotactic polystyrene main chain as defects. Whereas the m olecular structure of the styrene-ethylene copolymer produced over the TiCl4 catalyst seems to indicate that the styrene units are randomly distributed in the polyethylene main chain as defects. (C) 1998 Elsevi er Science B.V.