Synthesis of branched polypropylene with isotactic backbone and atactic side chains by binary iron and zirconium single-site catalysts

This article reports the use of a binary single-site catalyst system for synthesizing comb-branched polypropylene samples having isotactic polypropylene (iPP) backbones and atactic polypropylene (aPP) side chains from propylene feedstock. This catalyst system consisted of the bisiminepyridine iron catalyst ([2-ArN==C(Me)](2)C5H3N)FeCl2 [Ar = 2,6-C6H,(Me)(2)] (1) and the zirconocene catalyst rac-Me2Si(2-MeBenz[e]Ind)(2)ZrCl2 (2). The former in situ generated 1-propenyl-ended aPP macromonomer, whereas the latter incorporated the macromonomer into the copolymer. The effects of reaction conditions, such as the catalyst addition procedure and the ratio of 1/2 on the branching frequency, were examined. Copolymer samples having a branching density up to 8.6 aPP side chains per 1000 iPP monomer units were obtained. The branched copolymers were characterized by C-13 NMR and differential scanning calorimetry. (C) 2003 Wiley Periodicals, Inc.