Cocatalyst effect in propylene polymerization reactions with post-metallocene catalysts

• Published in: European polymer journal Vol. 49; no. 1; pp. 147 - 155
• Main Authors: Rishina, L.A., Galashina, N.M., Gagieva, S.C., Tuskaev, V.А., Kissin, Y.V.
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 01-01-2013
• Subjects: Gel permeation chromatography; Molecular weight distribution; Nuclear magnetic resonance; Polypropylene; Post-metallocene catalysts; Propylene polymerization; Nuclear magnetic resonance; Molecular weight distribution; Post-metallocene catalysts; Polypropylene; Propylene polymerization; Gel permeation chromatography
• ISSN: 0014-3057; 1873-1945
• DOI: 10.1016/j.eurpolymj.2012.10.018

Replacement of a cocatalyst from methylalumoxane to a combination of AlEt2Cl and MgBu2 in three post-metallocene catalysts based on complexes I–III (Scheme 1) leads to much higher activity in propylene polymerization reactions and to the formation of new isospecific active centers operating according to the enantiomorphic stereocontrol mechanism. [Display omitted]
► Propylene polymerization reactions with post-metallocene catalysts (I–III) were studied. ► Bidentate Ti complexes were activated with two cocatalysts, MAO and AlEt2Cl/MgBu2. ► A change of cocatalyst from MAO to AlEt2Cl/MgBu2 leads to a much higher activity. ► The activity increase is caused by the formation of new active centers. ► The enantiomorphic stereocontrol mechanism for the new isospecific centers is offered.
Effect of cocatalysts on the performance of three post-metallocene catalysts based on complexes I–III in Scheme 1 is studied by comparing their activity in the presence of two cocatalysts, MAO and a combination of AlEt2Cl and MgBu2, in propylene polymerization reactions. The second cocatalyst produces significantly more active catalysts. Analysis of GPC, DSC and 13C NMR data for the polymers suggests that the activity increase is caused by the formation of new types of active centers. Some of the new centers are isospecific and operate according to the enantiomorphic stereocontrol mechanism.