Amorphous Elastomeric Ultra-High Molar Mass Polypropylene in High Yield by Half-Titanocene Catalysts.

Propylene polymerizations with different ketimide-modified half-titanocene catalysts, Cp'TiCl 2 (N=C t Bu 2 ) [Cp' = C 5 H 5 ( 1 ), C 5 Me 5 ( 2 ), Me 3 SiC 5 H 4 ( 3 )], with MAO as a cocatalyst, were investigated. The obtained polymers were studied in detail by determining their microstructure, molar masses, thermal, and mechanical properties. The Cp*-ketimide, (C 5 Me 5 )TiCl 2 (N=C t Bu 2 ) ( 2 ), exhibited higher catalytic activities than Cp'TiCl 2 (N=C t Bu 2 ) ( 1 , 3 ), yielding higher molar mass polymers, M w up to 1400 Kg/mol. All the synthesized polypropylenes (PP) are atactic and highly regioregular, with predominant rrrr pentads, especially PP prepared with catalyst 1 . Differential scanning calorimetry (DSC) established that the polymers are fully amorphous aPP, and no melting endotherm events are detected. Glass transition temperatures were detected between -2 and 2 °C. These polypropylenes have been established to be high-performance thermoplastic elastomers endowed with remarkably high ductility, and a tensile strain at break higher than 2000%.