Formation Mechanism of Monodisperse Polyetherimide Nanoparticles with a Particle Size of 55 nm Prepared by Using Electrostatic Spraying Technique

Polymer nanoparticles have long been of interest in both academic and industrial applications. Although Polyetherimide (PEI) is a high-performance thermoplastic with many advantages, so far only a few works have focused on studying the nanomaterialization of commercial PEI. Here, monodispersed PEI nanoparticles with a particle size ≈55 nm are successfully prepared for the first time through electrostatic spraying from PEI/n-methylpyrrolidone (NMP)  solutions. Monodisperse PEI nanoparticles can be obtained at PEI concentration of 1 wt.%, and when PEI concentration is 5 or 10 wt.%, the products are micrometer-scale aggregates of PEI nanoparticles. As PEI concentration increased to 15 or 20 wt.%, PEI beads, and fibers appeared. In addition, the formation mechanism of PEI nanoparticles are also thoroughly investigated by rheological characterization and SEM observation. During the electrostatic spraying process, phase separation would occur when the droplets are formed, and then PEI nanoparticles generated by phase separation would be distributed around the inner edge of the droplets, and subsequently attached to the collection plate for further evaporation. This study will provide guidance and reference for the preparation of polymer nanoparticles smaller than 100 nm.