Macromolecules, Vol.31, No.11, 3409-3416, 1998
Ethene/propene copolymerization with high product of reactivity ratios from a single center, metallocene-based catalytic system
Ethene and propene were copolymerized using a metallocene-based catalytic system, composed of rac-isopropylidenebis(3-tert-butylcyclopentadienyl) dichloride, and poly(methylalumoxane) (MAO). Ethene/propene copolymers were prepared in a broad range of chemical composition, from 17% to 92% as ethene molar content. The use of an isospecific metallocene allowed the preparation of bipolymers composed of ethene and propene with regioregular propene units inserted, in a single macromolecular chain, with the same enantioface, whereas the careful control of the polymerization conditions led to the preparation of copolymers with a very narrow distribution of the chemical composition. A careful analysis of the copolymers microstructure was performed, essentially aimed at the investigation of the comonomers distribution. A statistical treatment of the C-13 NMR data brought to the determination of the reactivity ratios (r(1) and r(2)) of the comonomers. Data are reported and discussed to demonstrate that a single center homogeneous catalyst is able to prepare ethene/propene copolymers with long sequences of both comonomers.
Keywords:ETHYLENE-PROPYLENE COPOLYMERS;ZIEGLER-NATTA CATALYSTS;OLEFIN COPOLYMERIZATION;METHYLALUMINOXANE CATALYST;PROPENE POLYMERIZATION;CP2ZRCL2 CATALYST;EPDM SYNTHESIS;TERPOLYMERIZATIONS;ELASTOMERS