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ESR studies on vanadocene/cocatalyst systems for ethylene polymerization
Author(s) -
Wang L.,
Zhang P. Y.,
Feng L. F.,
Ji B.,
Yuan Y. L.,
Pan J.,
Ye C. Y.,
Jiang S.,
Feng L. X.
Publication year - 2000
Publication title -
journal of applied polymer science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.575
H-Index - 166
eISSN - 1097-4628
pISSN - 0021-8995
DOI - 10.1002/1097-4628(20010214)79:7<1188::aid-app50>3.0.co;2-j
Subject(s) - methylaluminoxane , vanadium , cyclopentadienyl complex , ethylene , chemistry , polymerization , polymer chemistry , catalysis , inorganic chemistry , metallocene , photochemistry , organic chemistry , polymer
Three vanadocene–cocatalyst catalytic systems for ethylene polymerization—Cp 2 ZrCl 2 /Al 2 Et 3 Cl 3 [dichlorobis(η‐cyclopentadienyl)vanadium/ethylaluminumsesquichloride], Cp 2 ZrCl 2 /MAO [dichlorobis(η‐cyclopentadienyl)vanadium/methylaluminoxane] and Cp 2 ZrCl 2 /AlEt 3 [dichlorobis(η‐cyclopentadienyl)vanadium/triethylaluminum]—were monitored by electron spin resonance (ESR) spectroscopy. It was found that at least a certain kind of vanadium complex is formed after mixing dichlorobis(η‐cyclopentadienyl)vanadium with ethylaluminumsesquichloride. After introducing ethylene, a new kind of vanadium complex is detected by ESR. Ethylene can be polymerized by using a dichlorobis(η‐cyclopentadienyl)vanadium/ethylaluminumsesquichloride catalytic system. These results possibly indicate that the vanadium complex exists in the forms ClCp 2 VClEtAlCl 2 and ClCp 2 VClEtAlClEt, which are responsible for forming active centers. The Dichlorobis(η‐cyclopentadienyl)vanadium/methylaluminoxane and dichlorobis(η‐cyclopentadienyl)vanadium/triethylaluminum systems also were monitored by ESR. Completely different spectra were recorded compared to those of the dichlorobis(η‐cyclopentadienyl) vanadium/ethylaluminumsesquichloride system. Ethylene almost cannot be polymerized by the dichlorobis(η‐cyclopentadienyl)vanadium/methylaluminoxane and dichlorobis(η‐cyclopentadienyl)vanadium/triethylaluminum catalytic systems, showing that resultant vanadium complexes of dichlorobis(η‐cyclopentadienyl)vanadium/methylaluminoxane and dichlorobis(η‐cyclopentadienyl)vanadium/triethylaluminum catalytic systems are different from that arising from the dichlorobis(η‐cyclopentadienyl)vanadium/ethylaluminumsesquichloride system. Plausible mechanisms are suggested for this. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 79: 1188–1194, 2001