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Abstract: Different alkylaluminums (triethyl-, tri-iso-butyl-, n-trihexylaluminum) were tested as activator for the iron complex LFeCl2 (1) (L=2,6-bis[(2,4,6-trimethylphenylimino)ethyl]pyridine) in ethylene polymerization. Various polymerization temperatures and the molar ratios of Al/Fe prepared polyethylene (PE) with different molecular weights, molecular weight distributions, polymerization activities and polyethylene structures. Through the analysis of in situ UV–vis absorption spectra, ethylene polymerization results and prepared polyethylene structures, the distinctive behaviors of the catalytic system could result from a new applicable mechanism involving two different kinds of catalytic species LFeRCl (a) and LFeR2 (b) (R=Et, i-Bu or He), the ratio of which varied with changing Al/Fe mole ratio when alkylaluminums were used as activators. The catalytic species (a) with very high activity mainly produced linear PE with high molecular weight in the bimodal PE. The catalytic species (b) with low activity mainly produced branched PE of low molecular weight in the bimodal PE. [Copyright &y& Elsevier]

Combined iron (II) and nickel (II) olefin polymerization catalysts could produce a kind of PE having the characters of ideal bimodal PE with appropriate conditions and catalysts. In the ethylene homopolymerization with triethylalkylaluminum (AIEt3) as the activator, the prepared bimodal PE contained not only branched PE of high molecular weight, but also linear PE of low molecular weight. And the amounts of both fractions were similar. Ideal bimodal PE resin was prepared in one polymerization reactor. [ABSTRACT FROM AUTHOR]