Continuous Flow Synthesis of Polystyrene Nanoparticles via Emulsion Polymerization Stabilized by a Mixed Nonionic and Anionic Emulsifier

Conducting emulsion polymerization in continuous flow mode for polymer nanoparticle synthesis has the potential to improve productivity and reliability but has to face the fact that the emulsion is difficult to remain stable without stirring. In this work, a mixed nonionic–anionic emulsifier TX-100/SDBS (4:1) was found to perform much better in stabilizing pre-emulsion than anionic emulsifier SDBS and then was exploited in the microflow system to achieve reliable operation, controllable conversion, and continuous synthesis of nanoparticles with uniform size (PDI < 0.09). The reaction temperature could be elevated to 95 °C, and the emulsifier concentration could be decreased to 8.515 mM. The average size of the nanoparticles was facilely adjusted from 52 to 92 nm by changing the emulsifier concentration.