Ring-opening metathesis polymerization in emulsion

Ring-opening metathesis polymerization (ROMP) of norbornene (NBE), catalyzed by water-soluble ruthenium alkylidenes 1, RuCl2(PCy2(C5H10NMe2Cl))(2)(=CHPh), or 2, RuCl2(TPPTS)(2)(=CHCO2Et) (TPPTS = tris(3-sulfonatophenyl)phosphine, sodium salt), has been carried out in emulsion. Polynorbornene latexes (PNBE) can be obtained in high yields, in the absence of floc, and with high solids, if Dowfax is used as surfactant. The nucleation mechanism of the polymerization has been found to be a continuous homogeneous nucleation. The resulting polymer particles are formed of aggregates of small primary particles, stabilized by the highly ionized chain ends. Typical particle sizes are ranging from 50 to 100 nm, even at higher solids. Less strained olefins, such as cyclooctene, COE, and 1,5-cyclooctadiene, GOD, cannot be efficiently polymerized by catalysts 1 or 2. Nevertheless, these monomers are polymerized by a hydrophobic catalyst, 3, RuCl2(PCy3)(2)(=CHPh). To form colloidal objects, the catalyst is dispersed into water through the use of a miniemulsion technique. The miniemulsion is then fed with monomer, and after polymerization, a latex is obtained. Monomer conversion is moderate, but a latex is generated in the absence of floc.