A comparison of (n-butCp)2ZrCl2 and other simple metallocenes with bridged Et(Ind)2ZrCl2 and Me2Si(Ind)2ZrCl2 catalysts in ethene/propene copolymerization

Al-alkenyl-induced formation of long-chain branched polyethylene via coordinative tandem insertion and chain-transfer polymerization using (nBuCp)2ZrCl2/MAO systems: An experimental and theoretical study

“…Notably, the rheological characterization suggested that the LCB density of PE3 generated with the Zr-1 homogeneous catalyst was comparable to that of the PE prepared under similar reaction conditions with the EBTHI-based catalyst [21]; this indicates that Al-1 is an efficient LCB promoter regardless the nature of the metallocene involved (at least with the two systems we have studied so far). This is remarkable since Zr-1 is known to incorporate comonomers (i.e., 1-hexene) to a much lower extent than EBTHI systems [23,28]. It is proposed that the insertion of the octenyl group of Al-1 is facilitated by the formation of intermediary Zr/Al heterobimetallic species.…”

“…Notably, the rheological fingerprints of PE3 are comparable to those of the PEs synthesized under similar reaction conditions with the previously reported EBTHI/MAO/Al-1 system (Figure 2) [21]; this suggests that a similar LCB density can be achieved with the Al-alkenyl co-reactant, regardless of the metallocene employed. This is remarkable, considering the very different comonomer incorporation ability of the two catalysts (EBTHI >> Zr-1) [28]. Nevertheless, it has to be noted that the reactivity of Al-1 could significantly differ from that of a conventional comonomer (i.e.…”

“…2) It has been demonstrated that with Zr-1 the incorporation of such comonomers as 1hexene occurs to a much lower extent (ca. a half) as compared with bridged metallocene systems [22,23,24,28]. Thus, the insertion of the pending vinyl moiety of Al-1 reagent during the polymerization with Zr-1 could be more challenging than in the case of the previously investigated rac-{EBTHI}ZrCl 2 -based systems [21].…”

Ethylene−Propylene Copolymerization with 2-Arylindene Zirconocenes

“…A direct comparison of monomer sequence distributions in copolymers generated with bis(2-arylindenyl) catalysts and those generated with 3 /MAO ( r e r p = 0.5) shows that 3 /MAO generates a higher fraction of the alternating EPE and PEP triads than 1 /MAO and 2 /MAO (Figure ). Two other examples of r e r p > 1 for metallocenes include Chien's report of r e r p = 1.5 for Cp 2 HfCl 2 13 and Lehtinen and Löfgren's recent report of r e r p = 2.51−2.75 for Ind 2 ZrCl 2 /MAO . In contrast to 1 /MAO ( r e = 3.8−5.4) and 2 /MAO ( r e = 4.2−6.0), both of these systems have relatively high values for r e ( r e = 13 and 20, respectively), indicating a tendency to incorporate longer ethylene sequences.…”

Metallocenes for Ethene/Propene Copolymerizations with High Product of Reactivity Ratios

“…A r E r P of 2.8 ± 0.4 was obtained from the statistical approach. It appeared worthwhile to us to further investigate these peculiar ethene/1-olefin copolymerizations with a high product of reactivity ratios, as few other data are reported in the literature. 4f, Instead of embarking on undue speculations, we decided to collect more experimental data, to investigate how a single-center catalyst can allow the formation of long homosequences of two different comonomers, such as ethene and the 1-olefin, in the same macromolecular chain, prepared through an insertion polymerization substantially free from physical limitations.…”