Polymerizations of methyl methacrylate (MMA) monomer initiated by a novel Ni(II)a-benzoinoxime complex have been achieved under homogeneous conditions in the 25-608C temperature range. The activity for polymerization increases with reaction temperature and by carrying out the polymerization in solution of low-polarity solvents without any induction time. The obtained polymers have weight-average molecular weights about 10 5 and slight broad polydispersity indexes (2.2 M w /M n 3.3). Dependence of rate constants polymerization and decomposition of initiator (k app and k d , respectively) on temperature was investigated and activation parameters were computed from Arrhenius plot. 1 H-NMR analysis of PMMA revealed a syndio-rich atactic microstructure in agreement with conventional radical process. Radical scavenger TEMPO effect together with microstructure and molecular weight distributions data supported that the polymerization proceed via free radical mechanism.

Copolymerizations of methyl methacrylate (MMA) with 4-vinylpyridine (4VP) were performed from different monomer feed ratios in 1,4-dioxan at 308C under free radical initiation experimental conditions, using Ni(II)a-Benzoinoxime complex as initiator. The obtained copolymers (PMMA4VP) were examined by FTIR and 1 H NMR spectroscopies. The composition of these copolymers was calculated, using 1 H NMR spectra and elemental analysis. Monomer reactivity ratios were estimated from Fineman-Ross (FR, r m 5 0.550, r v 5 1.165) and Kelen-Tudos (KT, r m 5 0.559, r v 5 1.286) linearization methods, as well as nonlinear error in variables model (EVM) method using the RREVM computer program (RREVM, r m 5 0.559, r v 5 1.264). These values suggest that MMA-4VP pair copolymerizes randomly. 1 H NMR spectra provide information about the stereochemistry of the copolymers in terms of sequence distributions and configurations. These results showed that the age of the Ni complex has an impact not only on its activity towards polymerization reactions but also on the features of the corresponding copolymers, whereas the chemical composition was insensitive to this prominent factor. The mechanism of MMA-4VP copolymerization is consistent with a radical process as supported by microstructure and molecular weight distribution studies. Thermal behaviours of these copolymers were investigated by differential scanning calorimetry and thermogravimetric analysis.