AbstractThe copolymerization of monomethyl itaconate (M1) (4‐methyl 1‐hydrogen 2‐methylene‐succinate) with methyl methacrylate (M2) was studied in bulk and in ethyl acetate solution. The reactivity ratios were determined to ber1= 0,56 ± 0,02 andr2= 1,56 ± 0,05. The dependences of copolymerization rate and degree of polymerization on initiator concentration, total monomer concentration and composition of monomer feed were measured. The reaction order with respect to the initiator concentration was near to the theoretical one (0,5), while that with respect to the total monomer concentration was considerably higher than predicted by theory (1,0). It could be explained by the influence of transfer reactions and diffusion control of termination reactions. Transfer reactions contribute to the reaction order mainly at low monomer concentration, while the influence of the medium viscosity becomes predominant at high monomer conc