The effect of surfactant (sodium dodecyl sulfate) concentration on particle size, molar masses, glass transition, and tacticity of poly(methyl methacrylate) (PMMA) nanoparticles synthesized by semicontinuous heterophase polymerization under monomer-starved condition at constant monomer feeding rate is reported. Starved conditions are confirmed by the low amount of residual monomer throughout the reaction and by the fact that the instantaneous polymerization rate is similar to the feeding rate of monomer. Under these conditions, polymer particles in the nanometer range (20-30 nm) were obtained with narrow size distribution (1.07 < D w /D n < 1.18), depending of surfactant concentration. Final particle size diminishes as the surfactant concentration is increased. Glass transition temperatures and syndiotactic content (54%-59%) of the produced polymers are substantially higher than those reported for commercial and bulkmade PMMA. Molar masses are much lower than those expected from termination by chain transfer to monomer, which is the typical termination mechanism in 0-1 emulsion and microemulsion polymerization of this monomer.

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