Methyl methacrylate and butyl methacrylate were polymerized in oil-in-water microemulsions that were stabilized by sodium dodecyl sulphate (SIDS). A poly(N-acetylethylenimine) (PNAEI) macromer was also included in the recipe, as a cosurfactant and a comonomer. Polymerizations were initiated by UV-irradiation. The average diameters of latex particles, obtained by STM, were in the range of 17-200 nm. The experimental data evidenced that the particle size was mainly dependent on the SDS/PNAEI ratio. Polymerization yields were around 75-85%. The synthesized copolymers have viscosity average molecular weights in the range of 2.1-2.4 x 10(6) and glass transition temperatures of 38.0-43.5 degreesC, lower than those obtained without using PNAEI. The investigation by means of FTIR and H-1-NMR techniques revealed that PNAEI was incorporated into the nanoparticles. (C) 2001 Elsevier Science Ltd. All rights reserved.