Emulsion polymerization of methyl methacrylate using the reverse iodine transfer polymerization (RITP) technique

The targeted molecular weight poly (methyl methacrylate) [PMMA] latex was successfully prepared in the presence of 4,4-azobis(4-cyanopentanoic acid) (ACPA) and various surfactants using the reversible iodine transfer polymerization (RITP)-emulsion polymerization at 85 °C for 7 h in the absence of light. The properties of PMMA particles upon the various ratios of ACPA to iodine within the concentration ranges of ACPA (1.0-2.0 mmol) and iodine (0.1-1.0 mmol) with various surfactants were investigated by means of GPC, SEM and particle analyzer. The weight-average molecular weight and the conversion increased with the ratio of [ACPA]/[I2], but no correlation between the particle size and the [ACPA]/[I2] ratio was obtained. The initiator, ACPA, was important in the formation of PMMA spherical particles, while molecular iodine dominated in controlling the molecular weight, inhibition period and the conversion. In overall, the appropriate concentration of ACPA, iodine and anionic or anionic with non-ionic surfactants controls the targeted molecular weight less than 100,000 g/mol and the enhanced conversion higher than 90% along with particle stability.