In:
e-Polymers, Walter de Gruyter GmbH, Vol. 3, No. 1 ( 2003-12-1)
Abstract:
This paper describes the structural control of polyolefins achieved by using group 4 transition metal complex catalysts featuring a pair of phenoxy-imine chelate ligands (named FI catalysts). FI catalysts can produce very low to ultrahigh molecular weight polymers. For example, a Zr-FI catalyst bearing a cycloalkyl group on the imine-nitrogen with methylaluminoxane (MAO) activation is capable of selectively forming vinyl-terminated low molecular weight polyethylenes (M w 〈 5000) whereas a Zr-FI catalyst with a triethylsilyl group ortho to the phenoxyoxygen can generate ethylene/propylene amorphous copolymers with ultra-high molecular weights (M w 〉 10 000 000) when treated with i Bu 3 Al / Ph 3 CB(C 6 F 5 ) 4 . In addition, a Ti-FI catalyst, possessing an o-phenoxytrimethylsilyl group, with MAO can form highly syndiotactic polypropylenes ([rrrr] = 84%, T m = 140°C) via a chainend control mechanism. Conversely, upon activation with i Bu 3 Al / Ph 3 CB(C 6 F 5 ) 4 , a Hf-FI catalyst with a tert-butyl group ortho to the phenoxy-oxygen is able to produce high molecular weight isotactic polypropylenes ([mm] = 69%, T m = 124°C, M w = 412 000) via a site control mechanism. Therefore, FI catalysts have shown the ability to create various polyolefin architectures by simple variation of the central metal, the ligand structure and the co-catalyst.
Type of Medium:
Online Resource
ISSN:
1618-7229
,
2197-4586
DOI:
10.1515/epoly.2003.3.1.258
Language:
Unknown
Publisher:
Walter de Gruyter GmbH
Publication Date:
2003
detail.hit.zdb_id:
2060396-4
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