The role of physicochemical properties in the nanoprecipitation of cellulose acetate.

The cellulose acetate (CA) nanoparticles (NPs) were prepared via the nanoprecipitation technique. The effects of solvent mixture quality and order of addition on the size evolution of CA NPs were investigated. The size of CA NPs was reduced by decreasing the nonsolvent-solvent mixture interaction parameter (χ) and by increasing the polymer-solvent mixture interaction parameter (χ). The NPs prepared by the method of addition of the polymer solution to the nonsolvent were smaller than those prepared by addition of the nonsolvent to the polymer solution. The very small CA NPs with the diameter of 37 nm and very narrow PdI of 0.045 were fabricated without using any surfactant and charged groups. The role of surface tension and osmotic pressure forces on the formation of NPs were discussed. The formation mechanism of NPs could be assigned to the rapid polymer precipitation and solidification (vitrification) of the nuclei.