Surfactant free fabrication of polyimide nanoparticles

Polyimide nanoparticles are fabricated using a combined liquid-liquid phase separation and solvent/ nonsolvent mixing technology. This technology allows us to produce stable polyimide nanoparticles with tunable size without any surfactants. Selective solvation and electron pair donor/electron pair acceptor interaction are employed to stabilize nanoparticles. The formation of polyimide nanoparticles is governed by a nucleation-dominated process and therefore the particle size is controlled by the nucleation rate. A very high level of supersaturation can be attained under the intensive local motions induced by ultrasound, resulting in a very high nucleation rate. This effect is found extremely useful in the fabrication of sub-50-nm polyimide nanoparticles.