Metallocene-initiated polymerization supported

Initial absorption of MAO on the support with subsequent addition to metallocenes in a second step this is the procedure most commonly used. The washed catalysts are used in combination with additional MAO or other aluminum alkyls in polymerization (208-210). 

This interpretation explains why Ziegler, Ballard, and metallocene catalysts, which have a different initiation chemistry, can be supported on the same silicas, but display totally different kinetics (and much faster reactions) without a gradual rise in activity. It also explains how the kinetics of polymerization with a single Cr/silica catalyst can be so easily manipulated by the choice of the reaction temperature, the activation temperature, CO reduction (Figure 16), and incorporation of metal alkyls and poisons in the reaction mixture. 

Polymerization Ziegler-Natta, supported metal oxides such as PhiUps, Unipol and metallocene Stereospecific chain formation required weak interaction/complexation with any initiators/catalysts metal coordination complexes required... 

Subsequently, Sun and Garces [96] also reported the preparation of PP/clay nanocomposites by in situ polymerization with metallocene/clay catalysts. Recently, Wang and coworkers [97] used thermally treated naturally occurring palygorskite to support titanocene (CpaTiCla) catalyst. After activation by MAO, the supported catalyst initiated an in situ ethylene polymerization resulting in the exfoliated dispersion of the nanofibers into the polyethylene matrix. The activity of the supported catalyst was found to be even higher than its solution counterpart and the final PE/clay nanocomposite showed physical properties. 

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