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Various elastomeric polypropylenes (PPs) are synthesized through homogeneous propylene polymerization with metallocene catalyst (2-PhInd)2ZrCl2 in the presence of different cocatalyst mixtures: triethylaluminum (TEA)/methylaluminoxane (MAO) or triisobutylaluminum (TIBA)/MAO in the range of AlAlR3/AlMAO = 0.0-0.9. The cocatalyst formulation impacts the resultant polymer microstructure and the thermal and dynamic mechanical properties of the produced PPs. 13C NMR analysis of the polymers reveals essentially atactic PP, with mmmm = 7.9% , when AlAlR3/AlMAO = 0.0. The mmmm pentad content is maximized when AlAlR3/AlMAO = 0.8; for TIBA, mmmm = 23.5%; and for TEA, mmmm = 17.6%. Differential scanning calorimetry analysis and dynamic mechanical thermal analysis corroborate these findings. Specifically, Tm, Δ Hm, and Tg are essentially maximized under these conditions, and the minimum damping is observed for AlAlR3/AlMAO = 0.6-0.8. 1H NMR analysis of the mixtures of catalyst and cocatalysts (without monomer) shows very minor differences for [Zr]:AlAlR3 in the range of 1:1-1:5. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2013 [ABSTRACT FROM AUTHOR]

The effect of adding various aluminum alkyls (R = Et, i-Bu) on the polymerization of propylene is studied using a (2-PhInd)2ZrCl2 pre-catalyst. A mild deactivating effect is found upon addition of TIBA, whereas TEA shows a sharp deactivating effect. Increasing amounts of AlR3 results in a significant activity increase for TIBA, but an activity plateau for TEA. AlR3 imposes remarkably different effects on the molecular weight and stereochemical microstructure of polymers. As the TIBA concentration increases, $\overline {M} _{{\rm v}} $ increases at first, growing from 49 000 to 72 000, but subsequently drops to 40 000. For TEA, $\overline {M} _{{\rm v}} $ decreases sharply, plummeting from 49 000 to 17 000. Both TIBA and TEA increase the mmmm pentad content from 7.9 to 23.5% and 17.6%, respectively. [ABSTRACT FROM AUTHOR]

Polyethylene reactor alloys are synthesized through heterogeneous ethylene polymerization with a new type of Ziegler-Natta (ZN)/late transition metal (LTM) hybrid catalyst. The effect of various parameters including catalyst composition (LTM/ZN = 0.01, 0.02, 0.04), polymerization temperature (TP = 30, 30-60, 60 °C) and loading temperature (TL = 30, 60 °C) on catalyst activity, chain's vinyl content, viscosity average molecular weight ( Mv) and thermal properties are investigated. Two distinct melting peaks were observed in the ranges of 110-140 °C and 60-90 °C, indicating presence of two different lamellar structures. LTM/ZN ratio shifted melting peaks toward lower values. Rheological properties confirmed homogeneity of polymer blend's microstructure as they follow time temperature superposition. [ABSTRACT FROM AUTHOR]