C2-Symmetric Zirconocenes for High Molecular Weight Amorphous Poly(propylene)

Crystallization properties of elastomeric polypropylene from alumina-supported tetraalkyl zirconium catalysts

“…Also in these cases the polymers present a homogeneous distribution of tacticity, being fully soluble in diethyl ether. The elasticity is due to the high degree of entanglement, in the case of the high molecular weight atactic polypropylene [15,16], and to the crystallization of the very short isotactic sequences in a predominantly amorphous material, in the case of the poorly isotactic polypropylene [17,18], producing the physical crosslinks of the elastomeric network.…”

“…More recently, Resconi has developed a C 2v -symmetric ansa-zirconocene catalyst, that efficiently produces high molecular weight atactic polypropylene [15,16], and C 2 -symmetric catalysts, which produce poorly isotactic polypropylene [17], showing elastic properties. Also in these cases the polymers present a homogeneous distribution of tacticity, being fully soluble in diethyl ether.…”

Controlling the Microstructure of Isotactic Polypropene by C2‐Symmetric Zirconocene Polymerization Catalysts: Influence of Alkyl Substituents on Regio‐ and Stereocontrol

“…A similar structure with only one methyl in 3‐position already shows a decreased melting point compared to the one without. The disruptive effect of small 3‐alkyl groups on the isoselectivity of chiral bridged bisindenyl complexes is well known 35,45…”

Controlled synthesis of stereoblock polypropylene. New trends in the development of elastomers

“…These results indicate that this stereocontrol mechanism may be involved in the propylene polymerisation under the action of 2-aryl-substituted metallocenes. The synthesis of the high-molecular-mass elSBPP on catalysts with C 2 symmetry, 101 namely, rac-Me 2 C(3-Pr i Ind) 2 ZrCl 2 and rac-H 2 C(3-Pr i Ind) 2 ZrCl 2 , should also be mentioned. In the presence of MAO, at 50 8C in liquid propylene, these complexes (Al : Zr = 1000 ± 4000) actively {A & 2.5 kg PP (mmol Zr) 71 [C 3 H 6 ] 71 h 71 } form amorphous polypropylene with a molecular mass of 100 000 ± 160 000 g mol 71 and with a content of isotactic pentads of 15.6% for the former catalyst and 25.5% for the latter catalyst.…”