Synthesis and Microstructurral Study of Stereoblock Elastomeric Polypropylenes from Metallocene Catalyst (2-PhInd)2ZrCl2 Activated with Cocatalyst Mixtures

Abstract

Various elastomeric polypropylenes (PPs) are synthe-<br><br>sized through homogeneous propylene polymerization with met-<br><br>allocene catalyst (2-PhInd)2ZrCl2 in the presence of different<br><br>cocatalyst mixtures: triethylaluminum (TEA)/methylaluminoxane<br><br>(MAO) or triisobutylaluminum (TIBA)/MAO in the range of AlAlR3/<br><br>AlMAO ¼ 0.0–0.9. The cocatalyst formulation impacts the resultant<br><br>polymer microstructure and the thermal and dynamic mechanical<br><br>properties of the produced PPs.<br><br>13<br><br>C NMR analysis of the polymers<br><br>reveals essentially atactic PP, with mmmm ¼ 7.9%, when AlAlR3/<br><br>AlMAO ¼ 0.0. The mmmm pentad content is maximized when<br><br>AlAlR3/AlMAO ¼ 0.8; for TIBA, mmmm ¼ 23.5%; and for TEA,<br><br>mmmm ¼ 17.6%. Differential scanning calorimetry analysis and<br><br>dynamic mechanical thermal analysis corroborate these findings.<br><br>Specifically, Tm, DHm,and Tg are essentially maximized under<br><br>these conditions, and the minimum damping is observed for<br><br>AlAlR3/AlMAO ¼ 0.6–0.8.<br><br>1<br><br>H NMR analysis of themixtures of catalyst<br><br>and cocatalysts (without monomer) shows very minor differences<br><br>for [Zr]:AlAlR3 in the range of 1:1–1:5.V C 2012Wiley Periodicals, Inc.<br><br>J. Polym. Sci., Part A: Polym. Chem. 2013, 51,724–731