Abstract
Propene polymerization with isotactic (iso)-specific C2-symmetric rac-Me2Si(2-Me-Benz(e)-Ind)2ZrCl2 (1) and rac-Me2Si(2-Me-4-Ph-1-Ind)2ZrCl2 (2) were conducted under various conditions for achieving iso-specific living polymerization of propene. When Complex 1 was activated with trialkylaluminum-free modified methylaluminoxane (dMMAO) at −40 °C, the number-average molecular weight (Mn) linearly increased against the polymerization time to reach Mn = 704,000 within 15 min of polymerization, although the molecular weight distributions was broad (Mw/Mn < 3). Thus, it was found that quasi-living polymerization of propene proceeded in the 1-dMMAO system. The living nature of iso-polypropene was confirmed by the block copolymerization, where the Mn value increased from 221,000 to 382,000 after the addition of 1-octene to yield the block copolymer with a melting point of 150 °C.
Highlights
Polyolefins are widely used because of their good chemical and physical properties as well as inexpensiveness and light weight
Catalytic ability of C2 -symmetric rac-Me2 Si(2-Me-Benz(e)-Ind)2 ZrCl2 (1) and rac-Me2 Si(2-Me-4-Ph1-Ind)2 ZrCl2 (2) for propene polymerization was investigated in toluene at 0 ◦ C under an atmospheric pressure of propene using dMMAO as a cocatalyst with an [Al]/[Zr] ratio of 800 and 400
These results indicate that the block copolymerization proceeded
Summary
Polyolefins are widely used because of their good chemical and physical properties as well as inexpensiveness and light weight. The economical preparation of olefin block copolymers with the long chain iso-PP sequence remains one of the challenges in the field of polymerization catalysis. Such polymers are obtained by block copolymerization with iso-specific living polymerization catalysts. In the case of propene polymerization by Me2 Si(η1 -N-t Bu)(η4 -indenyl)TiMe2 activated with dMMAO in heptane at 0 ◦ C, deactivation occurred [25] These results suggest that the living character strongly depended on the combination of the organometallic complexes, activator, and solvent as well as the polymerization temperature. Block copolymerization of propene and 1-octene was achieved to give iso-PP-block-poly(propene-co-1-octene) by the sequential addition of the monomers
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