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.