Chapter 5: Ring-Opening Metathesis Polymerization with an Ultra- fast-initiating Ruthenium Catalyst

Ring-opening metathesis polymerization (ROMP) is one of the most widely used polymerizations. With the development of well-defined catalysts, such as (t-BuO)2(ArN)Mo=CH(t-Bu) (1), Cl2(PCy3)2Ru=CHPh (2), and Cl2(PCy3)(IMesH2)Ru=CHPh (3), more controlled polymer structures have been obtained by either living polymerization or chain transfer induced polymerization. However, these catalysts suffer from a number of limitations. This chapter describes ROMP with the recently developed catalyst 4 which solves many problems of catalysts 1-3. The first is described the living polymerization of norbornene and norbornene derivatives by catalyst 4 to produce polymers with very narrow polydispersity index (PDI) and good molecular weight control. It also promotes living ROMP of several monomers that previous catalysts had problems with. Lastly, syntheses of block copolymers are also described. In the second half of the chapter, ROMP of more challenging protic monomers are demonstrated. Amphiphilic block copolymers have been prepared by catalyst 4 which spontaneously undergo self-assembly into stable nanoparticles (1050 nm in radius) in non-hydrogen bonding solvents such as CH2Cl2 and CHCl3. Polymeric nanoparticles are characterized by NMR, GPC, DLS and SEM.