Aqueous Dispersions of Polypropylene and Poly(1-butene) with Variable Microstructures Formed with Neutral Nickel(II) Complexes

Polymerization of 1-olefins and the polymer microstructures formed have been studied intensly with early transition metal catalysts, and more recently with late transition metal cationic Ni(II) and Pd(II) diimine complexes.1,2 In contrast, while neutral Ni(II) polymerization catalysts are of general interest due to their specific functional group tolerance, they have been little studied for 1-olefin polymerization.3-5 The only notable study is Fink’s polymerization of C4 to C20 1-olefins (in a nonaqueous system) with an in situ catalyst [Ni0(cod)2]/(Me3Si)2N-P{d NSiMe3)2 that most likely contains neutral Ni(II) active sites. 2,ö-incorporation was observed exclusively.3-5 Polymer dispersions, that is aqueous dispersions of polymer particles with sizes of ca. 50 nm to 1 ím, are employed on a large scale e.g. for environmentally friendly coatings and paints.6 Catalytic synthesis of polymer dispersions is an attractive aim, as it can enable control of polymer microstructures, by contrast to currently practiced free radical emulsion polymerization.7-11 Moreover, 1-olefins in particular are not susceptible to radical polymerization due to stable radical formation.