Surfactant Concentration Regime in Miniemulsion Polymerization for the Formation of MMA Nanodroplets by High-Pressure Homogenization

This article focuses on the adequate surfactant concentration regime in which MMA droplets are stabilized sufficiently against coalescence during high-pressure homogenization but still no diffusion processes from droplets to micelles take place in the polymerization. Monomer miniemulsions with different surfactant concentrations were prepared with different energy inputs. Emulsions result that depend either on the surfactant concentration or on the energy input of the homogenization process. For both cases, the occupancy of the interface is compared as a function of the droplet size. It is shown that the surfactant concentration needed for the stabilization of a specified interface area decreases with increasing droplet size. For the dependence of droplet size on the energy input, it is shown that more surfactant can be applied before emulsion polymerization starts, but the applicable surfactant concentration is lower than the cmc and also depends on droplet size.