Polymerization of methyl methacrylate with V(acac)₃ and VOCl₃ in combination with methylaluminoxane

Abstract

The polymerization of methyl methacrylate (MMA) with V(acac), and VOCl, in combination with methylaluminoxane (MAO) was investigated. The obtained polymers have a relatively narrow molecular weight distribution (MJM,, < 13). It was found that the isotactic triad content of the polymers increases with increasing temperature and MAO/V and MAO/MMA mole ratios. The interaction between MMA and MA0 has an influence on the tacticity of radically (initiator AIBN) obained polymers: in presence of MA0 the fraction of isotactic triads (mm) is higher. The catalytic activity of MAOcontaining catalysts (V(acac),/MAO and VOCI,/MAO) was compared with that of AIEt,-containing catalysts (V(acac),/AlEt, and VOCI,/AIEt,). It was not much different, but for MA0 as cocatalyst the isotacticity of the resulting PMMA's was higher, and the polydispersity lower, than with AlEt, as cocatalyst.

Polymerization of methyl methacrylate with Nickel(II)α‐benzoinoxime complex

“…1 H‐NMR analysis of the polymers gave support to the nature of polymerization process, as already out lined. Indeed, as pictured in Figure 2, the obtained polymers had a syndio‐rich atactic microstructure in agreement with that of PMMA free radically prepared by conventional initiator like AIBN 28. The stereoregularities were calculated from the α‐methyl resonance triplet in the region 0.8–1.3 ppm.…”

“…Moreover, the yields increased steadily with raising temperature, but no gel effect occurred that should indeed lead to a sharp increase of the conversion.The Ni(II)α‐benzoinoxime has however only a moderate activity for polymerization even at the highest reaction temperature: about 16% conversion for 6 h at 60°C as compared to free radical conventional initiator like AIBN. In the contrary, lower conversions were observed at higher temperatures in MMA polymerizations mediated by both vanadium based catalysts V(acac) 3 and VOCl 3 in combination with MAO28 and bis(cyclopentadienyl) titaniumdichloride, (Cp 2 TiCl 2 ), complex 29. Undertaken studies focused on improving the yields of MMA polymerizations by addition of additives (accelerator) as well as Et 3 N led to a remarkable enhancement.…”