High molecular weight atactic polypropene synthesized with (?5-pentamethylcyclopentadienyl)tribenzyl titanium activated with MAO

Abstract

The half-titanocene (η5-pentamethylcyclopentadienyl)tribenzyl titanium (Cp*TiBz3) with methylaluminoxane (MAO) as the cocatalyst was employed to catalyze propene polymerization at ambient pressure. A novel atactic polypropene elastomer with a high molecular weight (Mw = 2 − 8 × 105) was produced. The effects of the polymerization conditions on the catalytic activity and polymer molecular weight are discussed. 13C NMR analysis confirmed that the catalyst system Cp*TiBz3/MAO produced atactic polypropenes, and the polymerization mechanism was in agreement with the Bernoullian process. The triad sequence distribution of the polymer was measured and found to be as follows: mm = 6.15%, mr = 40.87%, and rr = 52.98% (Bernoullian factor B = 1.03); this indicated that the insertion of propene with the catalyst system followed a chain-end control model. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 411–415, 2000