Abstract
Propylene polymerization was conducted with ansa-monocyclopentadienylamidodimethyltitanium complexes ([(η1-t-BuN)SiMe2(Cp)]TiMe2, Cp = C5Me4, 1; C9H6, 2) in heptane as solvent at 0°C in the presence of dried modified methylaluminoxane (dMMAO), from which free Me3Al and iBu3Al were reduced to ca. 0.1 mol%. The effects of cyclopentadienyl ligands on propylene polymerization were investigated under atmospheric pressure of propylene in a semi-batch system where the polymerization rate was followed by the amount of propylene consumed. System 2 showed almost the same consumption rate as that of system 1 in the initial stage, but the rate gradually decreased with increasing polymerization time. In contrast, the rate of system 1 gradually increased during the polymerization. The produced polymer in system 1 had high molecular weight (Mn = 143,600) and relatively narrow molecular weight distribution (Mw/Mn = 1.31). Furthermore, the number-average molecular weight of the polymer linearly increased in proportion to the polymer yield with keeping the number of polymer chains constant. Thus, it was found that quasi-living polymerization of propylene proceeded in the 1-dMMAO/heptane system. The 13C NMR measurement of polypropylenes obtained indicated that systems 1 and 2 produced syndiotactic-enriched and isotactic-enriched polymers, respectively.
Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
