Synthesis of crystallizable sydiotactic-atactic stereoblock polypropylene using a living polymerization system

Propylene polymerizations were conducted by [ t -BuNSiMe 2 (3,6- t -Bu 2 Flu)]TiMe 2 using dried modified methyaluminoxane as a cocatalyst in heptane, chlorobenzene (CB), and a mixture of heptane/CB (1:1 in volume) at 0°C. Postpolymerizations testified that the propylene polymerization proceeded in a living manner regardless of the solvent used. The heptane system gave highly syndiotactic crystalline polypropylene (PP), whereas the CB and heptane/CB mixture systems gave amorphous PP. After the first polymerization in heptane had been completed, the same amounts of propylene and CB were added for the second polymerization. This procedure gave the syndiotactic-atactic stereoblock PP with a melting point of 119°C.