Anionic/nonionic surfactants for controlled synthesis of highly concentrated sub-50 nm polystyrene spheres

Polystyrene nanospheres are of great importance in 3D hard templating along with many other fields like pharmaceuticals and coatings. Therefore, it is important to be able to prepare polystyrene beads with different sphere sizes that suit each application. In this work, the emulsion polymerization method was used to prepare monodispersed polystyrene (PS) spheres with an average size of 50 nm, using styrene monomer, sodium dodecyl sulfate (SDS) and polyvinylpyrrolidone (PVP) as surfactants, and potassium persulfate (KPS) as the initiator. The average size and size distribution of the PS spheres were controlled by optimizing the synthesis parameters such as the concentration of the monomer, initiator, and surfactant, the type of surfactant, and the time and temperature of polymerization. The shape, size, and size distribution of the prepared PS spheres were characterized using dynamic light scattering (DLS) and scanning electron microscopy (SEM). The preparation of perfectly spherical PS spheres as small as 50 nm with a narrow size distribution is obtained using 8% styrene with (5% SDS and 2% KPS of the styrene amount) at 90 °C, with the monomer and surfactant molar ratio and concentration and the polymerization temperature being the dominating factors that affect the PS bead size.