Catalytic aqueous polymerization of butadiene by the cobalt catalyst system [Co(C8H13)(C4H6)]/CS2 affords colloidally stable latices of highly crystalline syndiotactic 1,2-polybutadiene (Tm ) 190 °C, ∆Hc ) 60 J/g, Mw ∼ 105 g/mol, 97% 1,2, 3% 1,4-cis). Catalyst modification with reagents containing electrophilic carbon atoms (e.g., aromatic formamides) strongly decreases polymer crystallinity (T...