HOMOGENEOUS BINARY ZIRCONOCENIUM CATALYST SYSTEMS FOR PROPYLENE POLYMERIZATION .1. ISOTACTIC ATACTIC INTERFACIAL COMPATIBILIZED POLYMERS HAVING THERMOPLASTIC ELASTOMERIC PROPERTIES/

Polypropylene with thermoplastic elastomeric properties was synthesize d by homopolymerization of propylene using two metallocene catalysts o f different stereospecificities: rac-ethylenebis(1-eta(5)-indenyl)zirc onium dichloride or rac-dimethylsilylenebis(1-eta(5)-indenyl)zirconium dichloride as isospecific catalyst precursors and ethylenebis(9-eta(5 )-fluorenyl)zirconium dichloride as an aspecific precursor. The cataly sts formed by activation of the precursors with triphenylcarbenium tet rakis( pentafluorophenyl)borate and triisobutylaluminum exhibit a very high activity of 5 x 10(7) g of PP/([Zr][C3H6] h). Products ranging f rom tough plastomers to weak elastomers were obtained by varying the r atio of the two types of precursors. The polymers containing less than half of the isotactic fraction display excellent thermoplastic elasto meric properties, which is attributable to an interconnected crystalli ne superstructure in an amorphous continuum compatibilized and bound t ogether by a stereoblock copolymer at the interface against macrophase separation. Materials exhibiting elastic recoveries of 97-98%, which are relatively independent of elongation up to 500%, were obtained.