Influence of anionic and non-ionic surfactants on nanoparticle synthesis by solvent-free extrusion emulsification

This study examines the impact of surfactants on the mechanism of a new solvent-free extrusion emulsification (SFEE) technique. Two sets of surfactants were used in this work, three anionic (SDBS, Unicid 350, Calfax DB-45) and three non-ionic (Igepal CO-890, Brij 58, Synperonic F-108). Of the anionic surfactants, only SDBS and Calfax were found to create stable O/W emulsions with a polyester in the desired 100–200 nm size range; the latter requiring a lower molar concentration. Igepal CO-890 and Brij 58 resulted in only partial emulsification despite requiring higher molar loadings than their anionic counterparts to accomplish this outcome, with majority of the polymer leaving the extruder without phase inverting. The study reinforced previous findings that the dispersion stage (zone) controls the SFEE technique, and highlighted the importance of water affinity displayed by a surfactant species to compensate for high retarding viscous force for mixing water into the polymer melt.