Quasi-Living Polymerization of Propene with an Isotactic-Specific Zirconocene Catalyst

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.

Preparation of Well-Controlled Isotactic Polypropylene-Based Block Copolymers with Superior Physical Performance via Efficient Coordinative Chain Transfer Polymerization

“…The macroscopic properties of these promising block copolymers, which range from elastomers to plastics, depend on the volume fraction of the EPR block, and these copolymers have tremendous potential as compatibilizers, modifiers, additives, elastomers, and high-impact plastics. Although i PP-based block copolymers can be produced by high-pressure stopped-flow polymerization or oscillating metallocene-catalyst-promoted sequential polymerization, these two methods are extremely difficult to use at industrial scales. , The recent development of novel catalytic methods for stereoselective living or quasi-living polymerization has allowed the production of well-controlled block copolymers with semicrystalline i PP blocks (or syndiotactic PP blocks), rubbery ethylene- co -propylene blocks (or propylene- co -1-octene blocks), or semicrystalline polyethylene blocks. − For example, Coates and co-workers prepared PE/ i PP multiblock polymers with precise control over block length using a living, isoselective catalyst system; these investigators proved that when properly designed, the block copolymers form strong interfaces with commercial-grade PE and i PP . However, these well-defined materials have not yet found widespread commercial use, probably because the low catalytic efficiency (the precatalyst molecule can produce only one polymer chain) of these methods drives up the costs of high-volume production.…”