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The influence of the Ti 3+ species on the microstructure of ethylene/1‐hexene copolymers
Author(s) -
Chu KyungJun,
Soares Joao B. P.,
Penlidis Alexander,
Ihm SonKi
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(19990601)200:6<1298::aid-macp1298>3.0.co;2-h
Subject(s) - copolymer , ethylene , polymer chemistry , gel permeation chromatography , branching (polymer chemistry) , 1 hexene , reactivity (psychology) , methylaluminoxane , hexene , chemistry , metallocene , materials science , polymerization , organic chemistry , catalysis , polymer , medicine , alternative medicine , pathology
Copolymerization of ethylene and 1‐hexene was carried out with catalysts having isolated Ti 3+ and multinuclear Ti 3+ species. Carbon‐13 nuclear magnetic resonance spectroscopy ( 13 C NMR), crystallization analysis fractionation (CRYSTAF), and gel permeation chromatography (GPC) studies showed that the microstructure of ethylene and 1‐hexene copolymers strongly depends upon the structure of the Ti 3+ species. Isolated Ti 3+ species increase the relative reactivity of ethylene in copolymerizations and produce copolymers with high molecular weight and broad short chain branching distribution (SCBD), with a large ethylene‐rich fraction. Multinuclear Ti 3+ species increase the relative reactivity of 1‐hexene and produce copolymers with low molecular weight and broad SCBD, with a large rubbery ethylene/1‐hexene fraction. Comparative studies of the copolymer microstructure from isolated Ti 3+ and multinuclear Ti 3+ in combination with different cocatalysts, Al(CH 3 ) 3 , Al(C 2 H 5 ) 3 , and methylaluminoxane (MAO) were also carried out. Isolated Ti 3+ species in combination with MAO cause remarkable changes in the 1‐hexene incorporation rate and SCBD in comparison with Al(CH 3 ) 3 and Al(C 2 H 5 ) 3 , while multinuclear Ti 3+ species in combination with MAO do not affect as much the 1‐hexene incorporation rate. This difference may be related to the mechanism of active site formation between the different Ti 3+ structures and MAO.