Synthesis of Stereoblock Polypropylene by Change of Temperature in Living Polymerization
[t-BuNSiMe2(3,6-t-Bu(2)Flu)]TiMe2 (1) combined with trialkylaluminum-free modified methylaluminoxane (dMMAO) was used to induce the living polymerization of propylene in toluene at -20, 0, and 25 degrees C with control of the syndiospecificity. After the first polymerization at -20 degrees C, the same amounts of propylene were added at 25 degrees C for the second polymerization. The resulting PP was syndiotactic-rich (rr = 0.75), the value of which is the arithmetical average ((0.89 + 0.60)/2 = 0.745) of those produced at -20 and 25 degrees C. These results indicate the formation of the expected syndiotactic-atactic di-stereoblock PP.
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Graduate School of Engineering