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Chap._300019 - only by the use of transition metal...

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3.4 Polypropylene (isotactic, syndiotactic and atactic) It has been previously noted that transition metal coordination catalysts were originally employed by Ziegler in 1953 to effect the polymerization of ethylene. Natta extended the use of the catalysts to higher olefins and obtained isotactic polypropylene in 1954. The first commercial production of the polymer was by Montel in 1957. Polypropylene is now an important commercial polymer, being used principally in the injection moulding of diverse articles, such as luggage, sterilizable hospital equipment, storage battery cases, washing machine agitators, automobile trims and bumpers. PP fiber is widely used as the tufting material in carpet. * Preparation PP has been produced commercially
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Unformatted text preview: only by the use of transition metal coordination (Ziegler-Natta) polymerization. Transition Metal Coordination Catalyst CH 2 =CH -(CH 2-CH) -x CH 3 CH 3 * Mechanism of Stereospecific Placement Coordination initiator performs two function. First, they supply the species for polymerization. Second, the fragment of the initiator aside from the initiating portion has unique coordination powers. Coordination of this fragment with both the propogating chain end and the incoming monomer occurs so as to orient the monomer with respect to the growing chain end and bring about its stereospecific addition. In other words, the monomer is oriented and "held in position" by coordination during addition to the polymer chain....
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