For the first time, modelling of the binary copolymerization rate is presented as a function of the solvent quality. This modelling was performed using a set of constant parameters only, i.e. with exclusion of variables. As an example, the copolymerization rate of the comonomer system methylmethacrylate (MMA)/N-vinyl pyrrolid-2-one (NVP) is described in terms of solvents : N-methyl pyrrolid-2-one (NMP), methyl isobutyrate (MiB) and cyclohexane (c-hex) as a function of the monomer feed composition. The polymerizations were conducted at 60 degrees C with AIBN as initiator at a global monomer concentration of 0.4 moll(-1).