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Polymerization behavior of α ‐olefins with rac ‐ and meso ‐type ansa ‐metallocene catalysts: Effects of cocatalyst and metallocene ligand
Author(s) -
Naga Naofumi,
Shiono Takeshi,
Ikeda Tomiki
Publication year - 1999
Publication title -
macromolecular chemistry and physics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.57
H-Index - 112
eISSN - 1521-3935
pISSN - 1022-1352
DOI - 10.1002/(sici)1521-3935(19990701)200:7<1587::aid-macp1587>3.0.co;2-5
Subject(s) - propene , methylaluminoxane , metallocene , polymerization , tacticity , polymer chemistry , hexene , coordination polymerization , ziegler–natta catalyst , chemistry , polymer , materials science , catalysis , copolymer , solution polymerization , organic chemistry
Polymerizations of propene, 1‐butene and 1‐hexene were conducted with a mixture of rac ‐ and meso‐ [dimethylsilylenebis(2‐methylindenyl)]zirconium dichloride ( 1 ) combined with methylaluminoxane (MAO), triethylaluminium (AlEt 3 )/triphenylcarbenium tetrakis(pentafluorophenyl)borate ( 2 ) or triisobutylaluminium (Al i Bu 3 )/ 2 as a cocatalyst. The polymerization profiles of propene with rac ‐ 1 and meso ‐ 1 were determined from the rate of overall propene consumption and the fractions of isotactic and atactic polymers which were sampled during polymerization. An induction time to reach the maximum R p (rate of polymerization) followed by gradual decay was observed in the case of using the systems rac ‐, meso ‐ 1 –MAO and rac ‐ 1 –Al i Bu 3 / 2 . Besides, a rapid drop of R p from the initial value was found when using AlEt 3 / 2 . Molecular weights of the isotactic and atactic polymers sampled do not change during polymerization, and it is suggested that the change of [C*] (number of active centers) is reflected in the profiles of R p . The rate ratio of rac ‐ 1 to meso ‐ 1 ( R p ( rac )/ R p ( meso )) in propene and 1‐butene polymerizations decreases in the following order: AlEt 3 / 2 > Al i Bu 3 / 2 > MAO. In the case of 1‐hexene polymerization, the highest R p ( rac )/ R p ( meso ) value was obtained. This result indicates that the coordination of 1‐hexene to the sterically hindered site of meso ‐ 1 is difficult compared with propene and 1‐butene.