Living alkene polymerization.
Here we present the development of a new class of polymn. catalysts, that combine the advantages of stereocontrolled and living polymn. of styrene. Stereocontrolled anionic (living) polymn. of styrene not only enables control over mol. wt. distributions of polymers with high tacticity, but also allows the synthesis of new hitherto unknown materials (i.e. block copolymers based on highly cryst. polystyrene). Our novel polymn. initiators are based on the heavier maingroup II metals (Ca, Sr and Ba) and are isolobal to the Group IV catalysts used in the com. prodn. of syndiotactic polystyrene. Stereocontrol during the polymn. is obtained via a chain-end control mechanism. Not only the stereospecific coordination of the styrene monomer to the metal but esp. the configurational stability of the chiral carbanionic chain-end is of utmost importance for stereocontrolled living polymn. of styrene.
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