Polymer syntheses that can be performed in environmentally friendly aqueous
media are of current interest. Aqueous emulsion polymerization already is
used in industry to make coatings and dyestuffs. It would be desirable to
extend such methods to metallocene catalysts, which offer a high degree of
structural control in the polymerization of olefins, but metallocene
complexes are very electrophilic and have to be handled in strictly water-
free environments.

Manders et al. now demonstrate that titanium metallocenes can be used in
the emulsion polymerization of styrene. In their system, the catalyst is
encapsulated, and thus shielded from water, during a pre-polymerization
step. It remains sufficiently accessible to the styrene monomers so that
the bulk of the polymer is produced within the emulsified droplet. -- JU

Angew. Chem. Int. Ed. 40, 4006 (2001).