Polymerization of acrylates and bulky methacrylates with the use of zirconocene precursors: Block copolymers with methyl methacrylate

The polymerization behavior of cyclohexyl methacrylate and trimethyl-silyloxyethyl methacrylate with the catalytic system Cp ₂ZrMe₂/B(C₆F₅)₃/ZnEt ₂ was examined. Block copolymers of these bulky methacrylates with methyl methacrylate (MMA), having high molecular weights and relatively narrow molecular weight distributions, were prepared. n-Butyl acrylate and tert-butyl acrylate were polymerized with various catalytic systems based on zirconocene complexes. These polymerizations seemed to proceed to a nonquantitative yield, producing polymers with high molecular weights and relatively low polydispersities. This behavior indicated the presence of termination reactions in the initiation step, which appeared to be faster than the propagation step. Block copolymers of these acrylates with MMA were synthesized with the catalytic system rac-Et(Ind)₂ZrMe₂/[B(C₆F ₅)₄]^-[Me₂NHPh]⁺/ZnEt ₂, starting from the polymerization of MMA. The block copolymers produced were well defined in most cases, as indicated by size exclusion chromatography, NMR, and differential scanning calorimetry measurements.