Influence of Indenyl Ligand Substitution Pattern on Metallocene-Catalyzed Ethene Copolymerization with 1-Octene

Abstract

The influence of silylene-bridged bis(indenyl) ligand substitution, especially benzannelation and 2-methyl substitution, on methylaluminoxane-activated metallocene-catalyzed ethene/1-octene copolymerization in toluene at 40 °C was investigated. 2-Methyl substitution gave significantly higher molecular masses at the expense of catalyst activity, whereas benzannelation promoted 1-octene incorporation and randomness of the resulting poly(ethene-co-1-octene) copolymers. Force field calculations based on steric arguments were used to explain experimental copolymerization results. Activation energy differences between ethene and 1-octene insertion accounted for improved 1-octene incorporation in the case of benzannelated metallocenes. According to 13 C-NMR microstructure analysis, copolymerization followed first-order Markov statistics.

Polyolefin nanocomposites formed by melt compounding and transition metal catalyzed ethene homo- and copolymerization in the presence of layered silicates

“…Metallocene-catalyzed ethene/1-octene copolymerization was reported in detail by Schneider and Suhm 16,17) . Typically, ethene polymerization catalyzed by MAO-activated zirconocene dichloride, rac-dimethlysilylenebis(2-methyl-benz[e]indenyl)zirconium dichloride (MBI) and N,N 9 -bis(2,6-diisopropylphenyl)-1,4-diaza-2,3-dimethyl-1,3-butadienenickeldibromide (DMN) catalysts were performed in a 1 L (1.6 L) mechanically stirred glass reactor (Büchi AG, Ulster/Switzerland).…”

Terminal and Penultimate Reactivity Ratios in Single‐Site Ethene/Propene Copolymerizations: Comparison of Kakugo and Direct Peak Methods

“…[9,16] The influence of 4-phenyl or benz[e] indenyl substitution on the copolymerization parameters compared to the unsubstituted catalysts 1 and 2 is remarkable in the sense that the difference in reactivity between ethylene and propylene is reduced significantly. Whereas catalysts 1 and 2 tend to incorporate the monomers in an alternating fashion, the other catalysts display a tendency to a more blocky incorporation, in line with previous results on catalysts 1, 2 and 4 obtained by Busico et al [4] Fink et al [2] proposed that such a tendency towards blockiness might originate from the effect of the bulkiness of the ultimate monomeric units on the more open or closed arrangement of the p-ligand system of the metallocene.…”

“…Mülhaupt et al observed a similar effect of the indenyl substitution pattern when using catalysts 1, 2, 5 and 6 in ethylene-1-octene copolymerizations and explained this behavior by making use of calculated relative activation energies for the ethylene and 1-octene insertions. [16] In ref. [17] a similar attempt is made for these catalysts for ethylene propylene copolymerizations, although only with minor success in reproducing the observed trends.…”

Metallocenes

“…Yet, counter to predictions from steric considerations alone, increasing aromatic rings trends slightly toward more comonomer incorporation. In ethylene-1-octene copolymerization, 2 ZrCl 2 /MAO incorporates more comonomer than does rac-(CH 3 ) 2 Si(Ind) 2 ZrCl 2 /MAO, despite the greater bulk of the benzannelated ligand (201).…”