Copolymerization of ethylene with α-olefins over supported titanium–magnesium catalysts. II. Comonomer as a chain transfer agent

Journal of Applied Polymer Science, Volume 125, Issue 3, pages 2042–2049, 5 August 2012

Copolymerization of ethylene with α-olefins over supported titanium–magnesium catalysts. II. Comonomer as a chain transfer agent

Marina I. Nikolaeva*, Mikhail A. Matsko, Tatiana B. Mikenas, Ludmila G. Echevskaya, Vladimir A. Zakharov

Boreskov Institute of Catalysis, Siberian Branch of the Russian Academy of Science, Pr. Akademika Lavrentieva, 5 Novosibirsk 630090, Russia

Email: Marina I. Nikolaeva

nikami@catalysis.ru

Abstract

Researchers obtained data on the effect of comonomer (propylene and 1-hexene) on molecular weight (Mw), molecular weight distribution (MWD), and content of terminal double bonds for ethylene/α-olefin copolymers produced over a supported titanium–magnesium catalyst (TMC) upon polymerization in the absence of hydrogen.

The data were used to calculate the ratios between the effective rate constants of chain transfer with monomer and the propagation rate constant.  Authors show that the effective rate constant of chain transfer with monomers increases in the row of monomers: ethylene < 1-hexene < propylene.  Data on the effect of copolymers on content of terminal double bonds of various types demonstrate that different reactions of chain transfer with comonomer may simultaneously occur during copolymerization. It results in simultaneous formation of terminal vinylidene and trans-vinylene bonds. Consequently, the calculated rate constants of chain transfer with comonomer are complex values, which include the rate constants of chain transfer with comonomer occurring via different mechanisms.

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