Homogeneous binary zirconocenium catalysts for propylene polymerization. II. Mixtures of isospecific and syndiospecific zirconocene systems

iPP–sPP Stereoblocks or Blends? Studies on the Synthesis of Isotactic–Syndiotactic Polypropylene Using Single C1‐Symmetric {Ph2C‐(Flu)(3‐Me3Si‐Cp)}ZrR2 Metallocene Precatalysts

“…Przybyla and Fink[3d] have proposed that the existence of stereo­block iPP− b −sPP segments can be diagnosed by an increase of intensities of the mrrr , mmrr, and mmmr pentads (representing junctions between isotactic and syndiotactic stereoblocks) with respect to those for individual i PP and s PP homopolymers. [3d] For catalyst systems based on 1b and 2b , the intensities of the mmrr and mmmr pentads perfectly fit the statistical model (Table , entries 5–9), while those of the mrrr appeared somewhat superior .…”

“…Przybyla and Fink[3d] have proposed that the existence of stereo­block iPP− b −sPP segments can be diagnosed by an increase of intensities of the mrrr , mmrr, and mmmr pentads (representing junctions between isotactic and syndiotactic stereoblocks) with respect to those for individual i PP and s PP homopolymers. [3d] For catalyst systems based on 1b and 2b , the intensities of the mmrr and mmmr pentads perfectly fit the statistical model (Table , entries 5–9), while those of the mrrr appeared somewhat superior . Thus, the higher content of rrrr and mrrr racemic pentads observed in the polymers produced with 1b and 2b , as compared with that derived from the statistic model, may stem from the presence of relatively long syndiotactic blocks either in a linked form (stereoblock copolymer) or in a form of s PP homopolymer impurities (blend of two homotactic polymers).…”

Alkyl exchange reaction between dialkylzinc compounds and methylaluminoxane and the effect on propylene polymerization

“…To investigate the detailed structure of end groups of polymers, 13 C NMR spectra were measured before and after the oxidation procedure (Fig. 3).…”

“…Room temperature 1 H NMR spectra were recorded on a Bruker Avance 400 instrument. High-temperature 1 H and 13 C NMR spectra were carried out in o-dichlorobenzene-d 4 (99.5% isotopic) at 390 K using a Bruker DMX 300 spectrometer (the left peak of the solvent was referenced at 7.22 ppm for 1 H NMR and 132.98 ppm for 13 C NMR). The molecular weight and molecular weight distribution of the polymers were determined by gel permeation chromatography (GPC) using a Waters Alliance GPC 2000 instrument equipped with a refractive index (RI) detector and a set of u-Styragel HT columns of 10 6 , 10 5 , 10 4 and 10 3 pore size in series.…”

Synthesis of elastomeric polypropylene in bulk using C 1-symmetric ansa-metallocenes. New aspects of the synthesis of 1-(fluoren-9-yl)-2-(2-methyl-5,6-dihydrocyclopenta [f]-1H-inden-1-yl)ethane and complexes of zirconium and hafnium with this ligand

“…Isomeric 1 (fluoren 9 yl) 2 (2 methyl 5,6 dihydrocyclopenta[ f ] 1H indenyl)ethanes 1a,b and C 1 symmetric metallocenes, viz., rac {1 (η 5 fluoren 9 yl) 2 (2 methyl 5,6 dihydro cyclopenta[ f ] η 5 inden 1 yl)ethane}zirconium dichloride (9) and rac {1 (η 5 fluoren 9 yl) 2 (2 methyl 5,6 dihydrocyclopenta[ f ] η 5 inden 1 yl)ethane}hafnium dichloride (10), with these ligands were synthesized by modified procedures. The structures of compounds 1b (two crystalline modifications) and 10 were established by X ray diffraction analysis.…”