Effect of surfactant concentration on the synthesis of poly(methyl methacrylate) nanoparticles by semicontinuous heterophase polymerization

Abstract

The effect of surfactant (sodium dodecylsulfate) concentration on the semi continuous heterophase polymerization of methyl methacrylate (MMA) is reported. Monomer starving conditions were achieved by adding semi continuously monomer at very low addition rates. These conditions were confirmed by the low amount of residual monomer throughout the reaction and by the fact that the instantaneous polymerization rate is similar to the monomer-dosing rate. Under these conditions polymer particles in the nanometer range were obtained with narrow size distribution (1.07 < Dw/Dn < 1.18). Final particle size increased from 23 to ca. 32 nm as the initial surfactant concentration decreased from 5 to 1 wt. %. Molecular masses are independent on surfactant concentration and they 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.