Effect of internal electron donor on the active center distribution in MgCl2-supported Ziegler–Natta catalyst

Abstract

1-Hexene polymerizations catalyzed by three kinds of MgCl2-supported Ziegler–Natta catalysts respectively, in which Cat-1 contains no internal donor (ID), Cat-2 contains diethylphthalate as ID, and Cat-3 contains anisole as ID, were quenched by cinnamoyl chloride to label the propagation chains. The effects of ID on active centers (C⁎) distribution and reactivity of different C⁎ were studied. Diethylphthalate significantly reduced the number of all kinds of C⁎, with those producing medium to high Mw polymer which were reduced more. Anisole significantly reduced the number of C⁎ producing medium to high Mw polymer, but slightly affected those producing low Mw polymer. Both IDs greatly enhanced the reactivity of C⁎ in the medium to high Mw fractions, while they slightly changed the properties of C⁎ producing low Mw polymer. Possible mechanisms of these ID effects are discussed.