Single-electron transfer living radical polymerization (SET-LRP) has developed as a reliable, robust and straight forward method for the construction well-defined polymers. To span an even larger variety of functional monomers, we investigated the copolymerization of methyl methacrylate with methacrylic acid by SET-LRP. Copolymerizations were catalyzed by Cu(0)/Me-6-TREN and performed in MeOH/H2O mixtures at 50 degrees C. The SET-LRP copolymerizations of varying methacrylic acid content were evaluated by kinetic experiments. At low (2.5%) and moderate (10%) MAA loadings, the copolymerizations obeyed perfect first order kinetics (k(p)(app) = 0.008 min(-1) and k(p)(app) = 0.006 min(-1)) and exhibited a linear increase in molecular weights with conversion providing narrow molecular weight distributions. The SET-LRP of MMA/25%-MAA was found to be significantly slower (k(p)(app) = 0.0035 min(-1)). However, a reasonable first-order kinetics in monomer consumption was maintained, and the control of the polymerization process was preserved since the molecular weight increased linearly with conversion and could therefore be adjusted. This work demonstrates that the copolymerization of methacrylic acid by SET-LRP is feasible and the design of well-defined macromolecules comprising acidic functionality can be achieved. (C) 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 4884-4888, 2010