A mechanistic study of the formation of polymer nanoparticles by the emulsification-diffusion technique

Abstract

The mechanism of formation of polymer nanoparticles prepared by the emulsification-diffusion method was evaluated under different preparation conditions and by turbidimetry measurements. Biodegradable poly (D,L-lactic acid) was used as the polymer model. The results show that each emulsion droplet will form several nanoparticles and that the interfacial phenomena during solvent diffusion determine the size properties of the resulting colloid particles. These phenomena cannot be entirely explained by the convection effects caused by interfacial turbulence. We suggest that nanoparticle formation is due to diffusion alone, and we propose a mechanism based on the “diffusion-stranding” mechanism for spontaneous emulsification. In this mechanism, the diffusion of solvent causes local supersaturation near the interface, and nanoparticles are formed, due to the phase transformation and polymer aggregation that occur in these regions. This interpretation is supported by the turbidity measurements made at different polymer concentrations and stirring rates.