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

Propylene polymerizations with different ketimide-modified half-titanocene catalysts, Cp'TiCl₂(N=CtBu₂) [Cp' = C₅H₅ (1), C₅Me₅ (2), Me₃SiC₅H₄ (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, (C₅Me₅)TiCl₂(N=CtBu₂) (2), exhibited higher catalytic activities than Cp'TiCl₂(N=CtBu₂) (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%.