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)]2C5H3N}FeCl2 [Ar = 2,6‐C6H3(Me)2] (1) and the zirconocene catalyst rac‐Me2Si(2‐MeBenz[e]Ind)2ZrCl2 (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 13C NMR and differential scanning calorimetry. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 1152–1159, 2003 A binary catalyst system consisting of a bisiminepyridine iron catalyst {[2‐ArNC(Me)]2C5H3N}FeCl2 [Ar = 2,6‐C6H3(Me)2] (1) and a zirconocene catalyst rac‐Me2Si(2‐MeBenz[e]Ind)2ZrCl2 (2) was used to synthesize isotactic polypropylene grafted with atactic polypropylene with propylene as the sole monomer. In the system, catalyst 1 in situ generated 1‐propenyl‐ended atactic polypropylene macromonomer, whereas catalyst 2 copolymerized propylene and the macromonomer to produce comb‐branched polypropylene with isotactic polypropylene backbone and atactic polypropylene side chains.