Polymerization of methyl methacrylate with the neutral zirconocene enolate Cp2ZrMe[OC(Me)=CMe2].
The polymn. of Me methacrylate (MMA) with the neutral enolate Cp2ZrMe[OC(OMe):CMe2] in the absence and in the presence of zirconocene cations Cp2ZrMe+ to bypass the rate-limited initiation of the system was investigated. Only by itself the enolate is not active in polymn., but as soon as the reaction system contains the cation, MMA is quant. converted into syndiotactic-rich PMMA with high mol. wt. (Mn > 100,000 g mol-1) and very narrow mol. wt. distribution (Mw/Mn < 1.05). The rate of polymn. was found to be first order referring to the neutral enolate and also referring to the cation. Rate coeffs. of all elementary reactions were detd. and compared to those obtained in a previous kinetic investigation of the polymn. using the initiator system Cp2ZrMe2/Ph3CB(C6F5)4. The agreement of both sets of calcd. coeffs. is satisfying. These results confirm that the mechanism of S. Collins et al. is suitable to describe the properties of the polymn. process.
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