(97d) Self-Assembling Process of Flash Nanoprecipitation in a Multi-Inlet Vortex Mixer

We present an experimental and numerical study of selfassembled polymeric nanoparticles in the process of flash nanoprecipitation using a multi-inlet vortex mixer (MIVM). The four-stream MIVM allows control of both the supersaturation and the final solvent quality by varying stream velocities. The design also enables the separation of reactive components prior to mixing. It is critical for the nanoprecipitation process to have a short mixing time, so that the solvent replacement starts homogeneously in the reactor. The properties of the nanoparticles depend on the competitive kinetics of polymer aggregation and organic solute nucleation and growth. We report the existence of a threshold Reynolds number (of 1600) over which nanoparticle sizes become independent of mixing. A similar value of the threshold Reynolds number is confirmed by numerical simulation along with experimental study of competitive reactions (the socalled “Bourne reactions”) in the MIVM. Flow patterns in the MIVM at various Reynolds number are microscopically visualized by mixing iron nitrate (Fe(NO₃)₃) and potassium thiocyanate (KSCN) to precipitate Fe(SCN)_x^(3-x).