New Half-Metallocene Catalysts Generating Polyethylene with Bimodal Molecular Weight Distribution and Syndiotactic Polystyrene

Aminosilylene-bridged ansa-zirconocenes for branched polyethylenes with bimodal molecular weight distributions

“…The former objective has been approached via copolymerization with higher a-olefins [3], the use of mono- [4] and bi-nuclear [5] ''constrained geometry catalysts", the use of meso ansa-metallocene-based catalysts [6], and homopolymerization with ''tandem catalytic systems" [7]. The latter goal has been tackled by using mixed metallocene systems [8], and by designing metallocene precatalysts that produce multi catalytically active species during the polymerization process [9][10][11]. In order to develop metallocene catalytic system that can simultaneously carry out both functions of the formation of branches and the modulation of the MWD, we have designed functionalized silylene-bridged ansa-zirconocenes 1-3.…”

Observation of bimodal polyethylene derived from TiO2-supported zirconocene/MAO catalyst during polymerization of ethylene and ethylene/1-hexene

“…Hence, the bimodal MW can provide both enhanced rheological and mechanical properties. In general, there are some techniques used to produce the bimodal MW polymer such as; (i) stepwise polymerization [9], (ii) polymerization using a mixture of two catalysts [10][11][12] for generating the dual sites, and (iii) a sudden variation of reaction conditions [13] for controlling the chain transfer reaction. In this present study, we revealed an alternative way to produce the bimodal PE with TiO 2 -supported zirconocene/MAO catalytic system.…”

Modified silicas as supports for single-site zirconocene catalysts

“…These bands are assigned to stretch- ing vibrations of C-H bonds of the methyl groups in MAO. In this way, the grafted MAO could activate the surface oxo-bonded zirconocenes of the neighbouring regions [16] by metal-siloxy bond cleavage, as observed in the molecular model [(C 5 H 9 ) 7 Si 7 O 12 ]ZrCp* [17]. This situation could lead to the formation of the potentially active alkylcationic surface species (Scheme 2).…”