Ethene/Propene Copolymerization with High Product of Reactivity Ratios from a Single Center, Metallocene-Based Catalytic System

Abstract

Ethene and propene were copolymerized using a metallocene-based catalytic system, composed of rac- isopropylidenebis(3- tert- butylcyclopentadienyl) zirconium 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 bi polymers 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 13 C 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.