POLYMERIZATION OF METHYL-METHACRYLATE WITH ACHIRAL 4B GROUP METALLOCENE COMPOUNDS

Methyl methacrylate (MMA) was polymerized with Cp(2)ZrCl(2)/methylaluminoxane or Cp(2)M(CH3)(2) (M: Zr, Hf; Cp = cyclopentadienyl) combined with B(C6F5)(3) (1) or Ph(3)CB(C6F5)(4) (2), (Ph = phenyl), in the presence of a Lewis acid like Zn(C2H5)(2). A quasi-living polymerization was promoted by Cp(2)Zr(CH3)(2)/2/Zn(C2H5)(2) with slow initiation, which gave syndiotactic-rich poly(methyl methacrylate) (PMMA) with high molecular weight. The polymer yield increases with polymerization time, which indicates that the propagation rate is zero order in concentration of monomer. The polymer yield increases also with concentration of Cp(2)Zr(CH3)(2)/2, which indicates the zirconocene to be the real catalyst. The polymer yield and the initiation efficiency (N/[Zr]) increase with the concentration of Zn(C2H5)(2), which indicates Zn(C2H5)(2) to be involved in the initiation. It is also shown that the propagation reaction is independent of the concentration of Zn(C2H5)(2).