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Ethylene Polymerizations with Alkyl‐, Disilylamino‐ and Cyclopentadienylchromium/MMAO Initiators
Author(s) -
Ikeda Haruhiko,
Monoi Takashi,
Ogata Keiji,
Yasuda Hajime
Publication year - 2001
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 - 10.1002/1521-3935(20010601)202:9<1806::aid-macp1806>3.0.co;2-a
Subject(s) - ethylene , chromium , metallocene , alkyl , polyethylene , polymer chemistry , catalysis , polymerization , chemistry , polymer , molar mass distribution , linear low density polyethylene , organic chemistry
The catalytic activities of non‐metallocene type chromium, half‐sandwich type chromium and metallocene type chromium complexes for the polymerization of ethylene were explored using MAO, modified MAO (MMAO) or BuAO in the presence or absence of a silica support. The complexes, Cr[N(SiMe 3 ) 2 ] 3 ( 1 ), Cr[CH(SiMe 3 ) 2 ] 3 ( 2 ), Cr(CH 2 SiMe 3 ) 4 ( 3 ), and Cr(CH 2 CMe 3 ) 4 ( 4 ), displayed good catalytic activities for the polymerization of ethylene in the presence of excess MAO or MMAO. The activities exceed 10 3 g‐PE/Cr‐mol·h to lead to polymers with M w > 80×10 4 . The molecular weight distributions are rather narrow in cases of complexes 1 and 2 . More efficient catalysis was observed when C 5 Me 4 ‐CH 2 CH 2 NMe 2 CrCl 2 ( 5 ) and C 5 H 4 CH 2 CH 2 N(iPr) 2 CrCl 2 ( 6 ) were used coupling with MMAO in the presence of a silica support. The M w increased to 276.2×10 4 and the M w / M w value decreased into 2.2 in the case of complex 5 . The catalysis of (C 5 H 5 ) 2 Cr ( 7 ) in the presence of a silica support is very high and the complex ( 7 ) produced high molecular weight polyethylene with narrow molecular weight distribution, while [1,3‐(SiMe 3 ) 2 C 5 H 3 ] 2 Cr ( 8 ) shows only a little catalytic activities presumably due to its very weak interaction with a silica support.